diff --git a/webapp/controller/UserController.class.php b/webapp/controller/UserController.class.php
index 67f35d87..c8234006 100644
--- a/webapp/controller/UserController.class.php
+++ b/webapp/controller/UserController.class.php
@@ -806,9 +806,15 @@ class UserController extends BaseAuthedController {
             die();
             return;
         }
-        User::Update(array(
-            'address' => $rspObj['data']['address']
-        ));
+        $address = strtolower($rspObj['data']['address']);
+        $oldUser = User::findByAddress($address);
+        if ($oldUser) {
+
+        } else {
+            User::Update(array(
+                'address' => $address
+            ));
+        }
         $propertyChgService = new services\PropertyChgService();
         $propertyChgService->addUserChg();
         $this->_rspData(array(