diff --git a/webapp/controller/ActivityController.class.php b/webapp/controller/ActivityController.class.php
index 563241b..29b9d0f 100644
--- a/webapp/controller/ActivityController.class.php
+++ b/webapp/controller/ActivityController.class.php
@@ -462,7 +462,7 @@ class ActivityController{
                     ' WHERE accountid=:accountid;',
                 array(
                     ':accountid' => $account_id,
-                    ':diamond_num' => $row['diamond_num'] - $cur_cost,
+                    ':diamond_num' => $userrow['diamond_num'] - $cur_cost,
                     ':modify_time' => time()
                 )
             );