diff --git a/webapp/models/InAppRecord.php b/webapp/models/InAppRecord.php
index 89e9c4d8..18b2b255 100644
--- a/webapp/models/InAppRecord.php
+++ b/webapp/models/InAppRecord.php
@@ -31,7 +31,7 @@ class InAppRecord extends BaseModel {
             ),
             array(
                 'amount' => function () use($amount) {
-                    return 'amount + ' + $amount;
+                    return 'amount + ' . $amount;
                 },
                 'buy_times' => function () {
                     return 'buy_times + 1';
@@ -60,7 +60,7 @@ class InAppRecord extends BaseModel {
             ),
             array(
                 'amount_ok' => function () use($amount) {
-                    return 'amount_ok + ' + $amount;
+                    return 'amount_ok + ' . $amount;
                 },
                 'buy_ok_times' => function () use($amount) {
                     return 'buy_ok_times + 1';