diff --git a/packages/io-ts-http/src/httpRoute.ts b/packages/io-ts-http/src/httpRoute.ts
index a2384299..f18aed71 100644
--- a/packages/io-ts-http/src/httpRoute.ts
+++ b/packages/io-ts-http/src/httpRoute.ts
@@ -13,8 +13,10 @@ export const Method = t.keyof({
 
 export type Method = t.TypeOf<typeof Method>;
 
+export type PathString = `/${string}`;
+
 export type HttpRoute<M extends Method = Method> = {
-  readonly path: string;
+  readonly path: PathString;
   readonly method: Uppercase<M>;
   readonly request: HttpRequestCodec<any>;
   readonly response: HttpResponse;
diff --git a/packages/superagent-wrapper/src/request.ts b/packages/superagent-wrapper/src/request.ts
index 41d9dd5e..3b53189e 100644
--- a/packages/superagent-wrapper/src/request.ts
+++ b/packages/superagent-wrapper/src/request.ts
@@ -201,7 +201,7 @@ export const requestForRoute =
     let path = route.path;
     for (const key in reqProps.params) {
       if (reqProps.params.hasOwnProperty(key)) {
-        path = path.replace(`{${key}}`, reqProps.params[key]);
+        path = path.replace(`{${key}}`, reqProps.params[key]) as h.PathString;
       }
     }