diff --git a/webapp/controller/ShopController.class.php b/webapp/controller/ShopController.class.php
index 18e9191..70399d0 100644
--- a/webapp/controller/ShopController.class.php
+++ b/webapp/controller/ShopController.class.php
@@ -296,6 +296,10 @@ class ShopController{
         $id = $_REQUEST['id'];
         $type = $_REQUEST['type'];
         $num = $_REQUEST['num'];
+        if ($num < 0) {
+            phpcommon\sendError(ERR_USER_BASE + 2,'没有这个商品');
+            return;
+        }
         $user_db = $this->readShopDB($account_id);
         $redis_goods = $this->getGoodsDiscount($id, $type, $user_db);
         $shop_conf = metatable\getShopById($type);