diff --git a/libs/sdk-js/src/auth/index.ts b/libs/sdk-js/src/auth/index.ts
index d93dd889a..cf995438d 100644
--- a/libs/sdk-js/src/auth/index.ts
+++ b/libs/sdk-js/src/auth/index.ts
@@ -27,10 +27,9 @@ export class Auth<
 
   on<T extends CallbackEvent>(event: T, callback: OnCallback<T, TUser>): this {
     this["~handlerCache"].callbacks ??= {};
-    const events = Array.isArray(event) ? event : [event];
+    const events: string[] = Array.isArray(event) ? event : [event];
     for (const event of events) {
-      this["~handlerCache"].callbacks[event as string] =
-        callback as AnyCallback;
+      this["~handlerCache"].callbacks[event] = callback as AnyCallback;
     }
     return this;
   }