diff --git a/bbb-webhooks/userMapping.js b/bbb-webhooks/userMapping.js
index 99fbc965e615ef321d47bdfff8db28bd6835800f..185e2fc9a4a5d247cde2859f5c7a3021dedf681c 100644
--- a/bbb-webhooks/userMapping.js
+++ b/bbb-webhooks/userMapping.js
@@ -127,7 +127,7 @@ module.exports = class UserMapping {
           result.push(undefined);
         }
       }
-      callback();
+      return (typeof callback === 'function' ? callback() : undefined);
     })();
   }