diff --git a/image-sharp/functions/index.js b/image-sharp/functions/index.js
index c56130001e..d60b5df3c2 100644
--- a/image-sharp/functions/index.js
+++ b/image-sharp/functions/index.js
@@ -88,6 +88,7 @@ exports.generateThumbnail = functions.storage.object().onChange((event) => {
     thumbnailUploadStream.on('finish', resolve).on('error', reject));
 
   return streamAsPromise.then(() => {
-    return console.log('Thumbnail created successfully');
+    console.log('Thumbnail created successfully');
+    return null;
   });
 });