diff --git a/packages/client-fetch/src/types.ts b/packages/client-fetch/src/types.ts
index fab60b8f4..a86578508 100644
--- a/packages/client-fetch/src/types.ts
+++ b/packages/client-fetch/src/types.ts
@@ -24,7 +24,8 @@ export interface Config<ThrowOnError extends boolean = boolean>
     | Record<string, unknown>
     | Array<Record<string, unknown>>
     | Array<unknown>
-    | number;
+    | number
+    | unknown;
   /**
    * A function for serializing request body parameter. By default,
    * {@link JSON.stringify()} will be used.