diff --git a/src/Gateways/MockerGateway.php b/src/Gateways/MockerGateway.php
index ee7ed83..ace7f5c 100644
--- a/src/Gateways/MockerGateway.php
+++ b/src/Gateways/MockerGateway.php
@@ -59,7 +59,7 @@ public function send()
     public function response($request)
     {
         $params = $request->all();
-        if($params['transaction_status'] == 'success'){
+        if(isset($params['transaction_status']) && $params['transaction_status'] == 'success'){
             $params['status'] = 'success';
             return $params;
         }