diff --git a/sdks/js-sdk/src/ApiClient.ts b/sdks/js-sdk/src/ApiClient.ts
index 16b5aa53f..eff85ac02 100644
--- a/sdks/js-sdk/src/ApiClient.ts
+++ b/sdks/js-sdk/src/ApiClient.ts
@@ -104,7 +104,7 @@ export type SubscriptionManager = {
   updateContentTopics?: UpdateContentTopics;
 };
 
-export type OnConnectionLostCallback = () => void;
+export type OnConnectionLostCallback = (err?: Error) => void;
 
 const isAbortError = (err?: Error): boolean => {
   if (!err) {