diff --git a/common/script/content/mystery-sets.js b/common/script/content/mystery-sets.js
index afdca2dbd1..7402b577f6 100644
--- a/common/script/content/mystery-sets.js
+++ b/common/script/content/mystery-sets.js
@@ -123,7 +123,7 @@ let mysterySets = {
 };
 
 each(mysterySets, (value, key) => {
-  return value.key = key;
+  value.key = key;
 });
 
 export default mysterySets;