diff --git a/app/assets/javascripts/discourse/models/user.js.es6 b/app/assets/javascripts/discourse/models/user.js.es6
index 49f314373dd..cc32dda9271 100644
--- a/app/assets/javascripts/discourse/models/user.js.es6
+++ b/app/assets/javascripts/discourse/models/user.js.es6
@@ -552,7 +552,7 @@ User.reopenClass(Singleton, {
   },
 
   checkUsername(username, email, for_user_id) {
-    return ajax(userPath('check_username') + ".json", {
+    return ajax(userPath('check_username'), {
       data: { username, email, for_user_id }
     });
   },