diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d13e1f7..480b5cd9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # next release  
 
+# 8.0.1  
+
+Fixes:  
+- Not working `customFetch` 
+  Error: `Failed to execute 'fetch' on 'Window': Illegal invocation`   
+
 # 8.0.0  
 
 BREAKING_CHANGES:  
diff --git a/package-lock.json b/package-lock.json
index 890ac917..15000de8 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "swagger-typescript-api",
-  "version": "8.0.0",
+  "version": "8.0.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 5d9a31a2..ae2bf656 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "swagger-typescript-api",
-  "version": "8.0.0",
+  "version": "8.0.1",
   "description": "Generate typescript/javascript api from swagger schema",
   "scripts": {
     "cli:json": "node index.js -r -d -p ./swagger-test-cli.json -n swagger-test-cli.ts",
diff --git a/templates/base/http-clients/fetch-http-client.eta b/templates/base/http-clients/fetch-http-client.eta
index b7bcf5c2..0dda48d3 100644
--- a/templates/base/http-clients/fetch-http-client.eta
+++ b/templates/base/http-clients/fetch-http-client.eta
@@ -31,7 +31,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
     baseUrl?: string;
     baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
     securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-    customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>
+    customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -52,7 +52,7 @@ export class HttpClient<SecurityDataType = unknown> {
     private securityData: SecurityDataType | null = null;
     private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
     private abortControllers = new Map<CancelToken, AbortController>();
-    private customFetch = fetch;
+    private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
     private baseApiParams: RequestParams = {
         credentials: 'same-origin',
diff --git a/tests/generated/v2.0/adafruit.ts b/tests/generated/v2.0/adafruit.ts
index d1a05171..296b54a2 100644
--- a/tests/generated/v2.0/adafruit.ts
+++ b/tests/generated/v2.0/adafruit.ts
@@ -192,7 +192,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -213,7 +213,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/another-example.ts b/tests/generated/v2.0/another-example.ts
index 05e5bbd3..80282bb4 100644
--- a/tests/generated/v2.0/another-example.ts
+++ b/tests/generated/v2.0/another-example.ts
@@ -168,7 +168,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -189,7 +189,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/another-schema.ts b/tests/generated/v2.0/another-schema.ts
index b3fdbbdc..43eaa01a 100644
--- a/tests/generated/v2.0/another-schema.ts
+++ b/tests/generated/v2.0/another-schema.ts
@@ -60,7 +60,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -81,7 +81,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/api-with-examples.ts b/tests/generated/v2.0/api-with-examples.ts
index 55cf244c..d838b0ac 100644
--- a/tests/generated/v2.0/api-with-examples.ts
+++ b/tests/generated/v2.0/api-with-examples.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/authentiq.ts b/tests/generated/v2.0/authentiq.ts
index e5512bc3..ad0bbf51 100644
--- a/tests/generated/v2.0/authentiq.ts
+++ b/tests/generated/v2.0/authentiq.ts
@@ -89,7 +89,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -110,7 +110,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/enums.ts b/tests/generated/v2.0/enums.ts
index 2c882efe..ea7c804c 100644
--- a/tests/generated/v2.0/enums.ts
+++ b/tests/generated/v2.0/enums.ts
@@ -102,7 +102,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -123,7 +123,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/example1.ts b/tests/generated/v2.0/example1.ts
index 00b4f427..03c08801 100644
--- a/tests/generated/v2.0/example1.ts
+++ b/tests/generated/v2.0/example1.ts
@@ -64,7 +64,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -85,7 +85,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/file-formdata-example.ts b/tests/generated/v2.0/file-formdata-example.ts
index fc6c0e78..3444d012 100644
--- a/tests/generated/v2.0/file-formdata-example.ts
+++ b/tests/generated/v2.0/file-formdata-example.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/furkot-example.ts b/tests/generated/v2.0/furkot-example.ts
index 6ae341d7..f1eb690c 100644
--- a/tests/generated/v2.0/furkot-example.ts
+++ b/tests/generated/v2.0/furkot-example.ts
@@ -100,7 +100,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -121,7 +121,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/giphy.ts b/tests/generated/v2.0/giphy.ts
index 4e51559c..4ba95720 100644
--- a/tests/generated/v2.0/giphy.ts
+++ b/tests/generated/v2.0/giphy.ts
@@ -319,7 +319,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -340,7 +340,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/github-swagger.ts b/tests/generated/v2.0/github-swagger.ts
index e5fa0292..93b4a85f 100644
--- a/tests/generated/v2.0/github-swagger.ts
+++ b/tests/generated/v2.0/github-swagger.ts
@@ -1472,7 +1472,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -1493,7 +1493,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/path-args.ts b/tests/generated/v2.0/path-args.ts
index 17de507d..a4d5ba97 100644
--- a/tests/generated/v2.0/path-args.ts
+++ b/tests/generated/v2.0/path-args.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore-expanded.ts b/tests/generated/v2.0/petstore-expanded.ts
index 9564fcb1..28732c1c 100644
--- a/tests/generated/v2.0/petstore-expanded.ts
+++ b/tests/generated/v2.0/petstore-expanded.ts
@@ -74,7 +74,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -95,7 +95,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore-minimal.ts b/tests/generated/v2.0/petstore-minimal.ts
index ab712307..8e06165f 100644
--- a/tests/generated/v2.0/petstore-minimal.ts
+++ b/tests/generated/v2.0/petstore-minimal.ts
@@ -45,7 +45,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -66,7 +66,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore-simple.ts b/tests/generated/v2.0/petstore-simple.ts
index 1a529ea2..4fb3ebdb 100644
--- a/tests/generated/v2.0/petstore-simple.ts
+++ b/tests/generated/v2.0/petstore-simple.ts
@@ -60,7 +60,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -81,7 +81,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore-swagger-io.ts b/tests/generated/v2.0/petstore-swagger-io.ts
index 2eac9a00..c86dceb2 100644
--- a/tests/generated/v2.0/petstore-swagger-io.ts
+++ b/tests/generated/v2.0/petstore-swagger-io.ts
@@ -105,7 +105,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -126,7 +126,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore-with-external-docs.ts b/tests/generated/v2.0/petstore-with-external-docs.ts
index 8997920e..521d40a2 100644
--- a/tests/generated/v2.0/petstore-with-external-docs.ts
+++ b/tests/generated/v2.0/petstore-with-external-docs.ts
@@ -50,7 +50,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -71,7 +71,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/petstore.ts b/tests/generated/v2.0/petstore.ts
index 5cabb1e9..005cb174 100644
--- a/tests/generated/v2.0/petstore.ts
+++ b/tests/generated/v2.0/petstore.ts
@@ -52,7 +52,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -73,7 +73,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/query-path-param.ts b/tests/generated/v2.0/query-path-param.ts
index c90add11..10b5a9dc 100644
--- a/tests/generated/v2.0/query-path-param.ts
+++ b/tests/generated/v2.0/query-path-param.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v2.0/uber.ts b/tests/generated/v2.0/uber.ts
index 97ef8720..b15c5839 100644
--- a/tests/generated/v2.0/uber.ts
+++ b/tests/generated/v2.0/uber.ts
@@ -132,7 +132,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -153,7 +153,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/additional-properties.ts b/tests/generated/v3.0/additional-properties.ts
index 6dab8d21..9792c373 100644
--- a/tests/generated/v3.0/additional-properties.ts
+++ b/tests/generated/v3.0/additional-properties.ts
@@ -44,7 +44,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -65,7 +65,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/additional-properties2.ts b/tests/generated/v3.0/additional-properties2.ts
index 35b11561..f82d0a6b 100644
--- a/tests/generated/v3.0/additional-properties2.ts
+++ b/tests/generated/v3.0/additional-properties2.ts
@@ -41,7 +41,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -62,7 +62,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/allof-example.ts b/tests/generated/v3.0/allof-example.ts
index 806224bb..e5fb76be 100644
--- a/tests/generated/v3.0/allof-example.ts
+++ b/tests/generated/v3.0/allof-example.ts
@@ -45,7 +45,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -66,7 +66,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/anyof-example.ts b/tests/generated/v3.0/anyof-example.ts
index b28443fb..6c6400d1 100644
--- a/tests/generated/v3.0/anyof-example.ts
+++ b/tests/generated/v3.0/anyof-example.ts
@@ -47,7 +47,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -68,7 +68,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/api-with-examples.ts b/tests/generated/v3.0/api-with-examples.ts
index 803cecff..c5b6c779 100644
--- a/tests/generated/v3.0/api-with-examples.ts
+++ b/tests/generated/v3.0/api-with-examples.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/callback-example.ts b/tests/generated/v3.0/callback-example.ts
index 0b2dbc46..d46d28fd 100644
--- a/tests/generated/v3.0/callback-example.ts
+++ b/tests/generated/v3.0/callback-example.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/components-responses.ts b/tests/generated/v3.0/components-responses.ts
index 19cb9986..e59635a5 100644
--- a/tests/generated/v3.0/components-responses.ts
+++ b/tests/generated/v3.0/components-responses.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/explode-param-3.0.1.ts b/tests/generated/v3.0/explode-param-3.0.1.ts
index 468ae1a0..407ed178 100644
--- a/tests/generated/v3.0/explode-param-3.0.1.ts
+++ b/tests/generated/v3.0/explode-param-3.0.1.ts
@@ -57,7 +57,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -78,7 +78,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/full-swagger-scheme.ts b/tests/generated/v3.0/full-swagger-scheme.ts
index bc16b2f2..3235cd80 100644
--- a/tests/generated/v3.0/full-swagger-scheme.ts
+++ b/tests/generated/v3.0/full-swagger-scheme.ts
@@ -8981,7 +8981,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -9002,7 +9002,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/link-example.ts b/tests/generated/v3.0/link-example.ts
index 0010ac2a..75386ce3 100644
--- a/tests/generated/v3.0/link-example.ts
+++ b/tests/generated/v3.0/link-example.ts
@@ -54,7 +54,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -75,7 +75,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/no-definitions-schema.ts b/tests/generated/v3.0/no-definitions-schema.ts
index 5bfef145..e807b4e9 100644
--- a/tests/generated/v3.0/no-definitions-schema.ts
+++ b/tests/generated/v3.0/no-definitions-schema.ts
@@ -50,7 +50,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -71,7 +71,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/nullable-refs.ts b/tests/generated/v3.0/nullable-refs.ts
index af503cd9..93bad182 100644
--- a/tests/generated/v3.0/nullable-refs.ts
+++ b/tests/generated/v3.0/nullable-refs.ts
@@ -51,7 +51,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -72,7 +72,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/oneof-example.ts b/tests/generated/v3.0/oneof-example.ts
index 404c3251..3289f9df 100644
--- a/tests/generated/v3.0/oneof-example.ts
+++ b/tests/generated/v3.0/oneof-example.ts
@@ -47,7 +47,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -68,7 +68,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/personal-api-example.ts b/tests/generated/v3.0/personal-api-example.ts
index 395d7f0c..ad4abbf9 100644
--- a/tests/generated/v3.0/personal-api-example.ts
+++ b/tests/generated/v3.0/personal-api-example.ts
@@ -238,7 +238,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -259,7 +259,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/petstore-expanded.ts b/tests/generated/v3.0/petstore-expanded.ts
index ba61ee3b..0a13266f 100644
--- a/tests/generated/v3.0/petstore-expanded.ts
+++ b/tests/generated/v3.0/petstore-expanded.ts
@@ -50,7 +50,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -71,7 +71,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/petstore.ts b/tests/generated/v3.0/petstore.ts
index b7ef4ddb..b525eb93 100644
--- a/tests/generated/v3.0/petstore.ts
+++ b/tests/generated/v3.0/petstore.ts
@@ -54,7 +54,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -75,7 +75,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/recursive-schema.ts b/tests/generated/v3.0/recursive-schema.ts
index 9d5a6cf5..75e11849 100644
--- a/tests/generated/v3.0/recursive-schema.ts
+++ b/tests/generated/v3.0/recursive-schema.ts
@@ -51,7 +51,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -72,7 +72,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/responses.ts b/tests/generated/v3.0/responses.ts
index 97611894..31153a5a 100644
--- a/tests/generated/v3.0/responses.ts
+++ b/tests/generated/v3.0/responses.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/swaggerhub-template.ts b/tests/generated/v3.0/swaggerhub-template.ts
index 033a48a0..fa09f432 100644
--- a/tests/generated/v3.0/swaggerhub-template.ts
+++ b/tests/generated/v3.0/swaggerhub-template.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/tsoa-odd-types-3.0.2.ts b/tests/generated/v3.0/tsoa-odd-types-3.0.2.ts
index b0268624..14a473ba 100644
--- a/tests/generated/v3.0/tsoa-odd-types-3.0.2.ts
+++ b/tests/generated/v3.0/tsoa-odd-types-3.0.2.ts
@@ -158,7 +158,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -179,7 +179,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/up-banking.ts b/tests/generated/v3.0/up-banking.ts
index b6e8417d..05977526 100644
--- a/tests/generated/v3.0/up-banking.ts
+++ b/tests/generated/v3.0/up-banking.ts
@@ -575,7 +575,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -596,7 +596,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/uspto.ts b/tests/generated/v3.0/uspto.ts
index 243072f7..2827cbd0 100644
--- a/tests/generated/v3.0/uspto.ts
+++ b/tests/generated/v3.0/uspto.ts
@@ -54,7 +54,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -75,7 +75,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/wrong-enum-subtypes.ts b/tests/generated/v3.0/wrong-enum-subtypes.ts
index f1a55537..24aa52fe 100644
--- a/tests/generated/v3.0/wrong-enum-subtypes.ts
+++ b/tests/generated/v3.0/wrong-enum-subtypes.ts
@@ -39,7 +39,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -60,7 +60,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/generated/v3.0/wrong-schema-names.ts b/tests/generated/v3.0/wrong-schema-names.ts
index 30f58c9f..1e23f51c 100644
--- a/tests/generated/v3.0/wrong-schema-names.ts
+++ b/tests/generated/v3.0/wrong-schema-names.ts
@@ -61,7 +61,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -82,7 +82,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/defaultAsSuccess/schema.ts b/tests/spec/defaultAsSuccess/schema.ts
index 49f3737b..0b6cef76 100644
--- a/tests/spec/defaultAsSuccess/schema.ts
+++ b/tests/spec/defaultAsSuccess/schema.ts
@@ -89,7 +89,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -110,7 +110,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/defaultResponse/schema.ts b/tests/spec/defaultResponse/schema.ts
index 64463587..cb24e38f 100644
--- a/tests/spec/defaultResponse/schema.ts
+++ b/tests/spec/defaultResponse/schema.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/enumNamesAsValues/schema.ts b/tests/spec/enumNamesAsValues/schema.ts
index 06f53e2d..be7bbf2c 100644
--- a/tests/spec/enumNamesAsValues/schema.ts
+++ b/tests/spec/enumNamesAsValues/schema.ts
@@ -235,7 +235,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -256,7 +256,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/extractRequestParams/schema.ts b/tests/spec/extractRequestParams/schema.ts
index d3de6026..ef7b6715 100644
--- a/tests/spec/extractRequestParams/schema.ts
+++ b/tests/spec/extractRequestParams/schema.ts
@@ -129,7 +129,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -150,7 +150,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/js/schema.d.ts b/tests/spec/js/schema.d.ts
index c4030348..33783a24 100644
--- a/tests/spec/js/schema.d.ts
+++ b/tests/spec/js/schema.d.ts
@@ -1727,7 +1727,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
   data: D;
diff --git a/tests/spec/js/schema.js b/tests/spec/js/schema.js
index 156726b9..ff508f2e 100644
--- a/tests/spec/js/schema.js
+++ b/tests/spec/js/schema.js
@@ -20,7 +20,7 @@ export class HttpClient {
     this.baseUrl = "https://api.github.com";
     this.securityData = null;
     this.abortControllers = new Map();
-    this.customFetch = fetch;
+    this.customFetch = (...fetchParams) => fetch(...fetchParams);
     this.baseApiParams = {
       credentials: "same-origin",
       headers: {},
diff --git a/tests/spec/modular/http-client.ts b/tests/spec/modular/http-client.ts
index 985d4401..7d6bf15d 100644
--- a/tests/spec/modular/http-client.ts
+++ b/tests/spec/modular/http-client.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/moduleNameFirstTag/schema.ts b/tests/spec/moduleNameFirstTag/schema.ts
index ef250ad5..4a2a8d28 100644
--- a/tests/spec/moduleNameFirstTag/schema.ts
+++ b/tests/spec/moduleNameFirstTag/schema.ts
@@ -165,7 +165,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -186,7 +186,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/moduleNameIndex/schema.ts b/tests/spec/moduleNameIndex/schema.ts
index 3f4ec33b..6e9d6f94 100644
--- a/tests/spec/moduleNameIndex/schema.ts
+++ b/tests/spec/moduleNameIndex/schema.ts
@@ -165,7 +165,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -186,7 +186,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/partialBaseTemplate/schema.ts b/tests/spec/partialBaseTemplate/schema.ts
index 381b89ae..9ed59710 100644
--- a/tests/spec/partialBaseTemplate/schema.ts
+++ b/tests/spec/partialBaseTemplate/schema.ts
@@ -49,7 +49,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -70,7 +70,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/partialDefaultTemplate/schema.ts b/tests/spec/partialDefaultTemplate/schema.ts
index a78115ce..0500edc3 100644
--- a/tests/spec/partialDefaultTemplate/schema.ts
+++ b/tests/spec/partialDefaultTemplate/schema.ts
@@ -45,7 +45,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -66,7 +66,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/responses/schema.ts b/tests/spec/responses/schema.ts
index d2d30a1c..d19646ba 100644
--- a/tests/spec/responses/schema.ts
+++ b/tests/spec/responses/schema.ts
@@ -89,7 +89,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -110,7 +110,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/singleHttpClient/schema.ts b/tests/spec/singleHttpClient/schema.ts
index 033b0640..93cc8cfc 100644
--- a/tests/spec/singleHttpClient/schema.ts
+++ b/tests/spec/singleHttpClient/schema.ts
@@ -37,7 +37,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -58,7 +58,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/typeSuffixPrefix/schema.ts b/tests/spec/typeSuffixPrefix/schema.ts
index 4a957753..3fbe8991 100644
--- a/tests/spec/typeSuffixPrefix/schema.ts
+++ b/tests/spec/typeSuffixPrefix/schema.ts
@@ -1482,7 +1482,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -1503,7 +1503,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",
diff --git a/tests/spec/unionEnums/schema.ts b/tests/spec/unionEnums/schema.ts
index 84a58df1..ff4461e8 100644
--- a/tests/spec/unionEnums/schema.ts
+++ b/tests/spec/unionEnums/schema.ts
@@ -49,7 +49,7 @@ export interface ApiConfig<SecurityDataType = unknown> {
   baseUrl?: string;
   baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
   securityWorker?: (securityData: SecurityDataType | null) => Promise<RequestParams | void> | RequestParams | void;
-  customFetch?: (input: RequestInfo, init?: RequestInit) => Promise<Response>;
+  customFetch?: typeof fetch;
 }
 
 export interface HttpResponse<D extends unknown, E extends unknown = unknown> extends Response {
@@ -70,7 +70,7 @@ export class HttpClient<SecurityDataType = unknown> {
   private securityData: SecurityDataType | null = null;
   private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
   private abortControllers = new Map<CancelToken, AbortController>();
-  private customFetch = fetch;
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) => fetch(...fetchParams);
 
   private baseApiParams: RequestParams = {
     credentials: "same-origin",