diff --git a/webapp/controller/ShopController.class.php b/webapp/controller/ShopController.class.php
index 386636b7..6751e282 100644
--- a/webapp/controller/ShopController.class.php
+++ b/webapp/controller/ShopController.class.php
@@ -1794,7 +1794,7 @@ class ShopController extends BaseAuthedController
         return $costItems;
     }
 
-    private function internalAddItem($propertyChgService, $itemMeta, $count, $sysAdd, $grade)
+    private function internalAddItem($propertyChgService, $itemMeta, $count, $sysAdd, $grade = null)
     {
         switch ($itemMeta['type']) {
             case mt\Item::HERO_TYPE: {