diff --git a/aws4/index.d.ts b/aws4/index.d.ts
index 88f54f2a3f..6028be5334 100644
--- a/aws4/index.d.ts
+++ b/aws4/index.d.ts
@@ -30,4 +30,4 @@ export class RequestSigner {
     formatPath(): string;
 }
 
-export function sign(options?: any, credentials?: any): RequestSigner;
+export function sign(options?: any, credentials?: any): any;