diff --git a/src/Message/CompletePurchaseResponse.php b/src/Message/CompletePurchaseResponse.php
index 1173f29..5a5e3fd 100644
--- a/src/Message/CompletePurchaseResponse.php
+++ b/src/Message/CompletePurchaseResponse.php
@@ -77,7 +77,7 @@ public function getSign()
      */
     public function getTransactionId()
     {
-        return $this->data['ik_inv_id'];
+        return $this->data['ik_pm_no'];
     }
 
     /**