diff --git a/lib/s3/managed_upload.d.ts b/lib/s3/managed_upload.d.ts
index 9cbebdb8eb..c1a2eb74a6 100644
--- a/lib/s3/managed_upload.d.ts
+++ b/lib/s3/managed_upload.d.ts
@@ -16,7 +16,7 @@ export class ManagedUpload {
     /**
      * Initiates the managed upload for the payload.
      */
-    send(callback?: (err: AWSError, data: ManagedUpload.SendData) => void): void;
+    send(callback?: (err: AWSError|null, data: ManagedUpload.SendData) => void): void;
     /**
      * Adds a listener that is triggered when theuploader has uploaded more data.
      *