diff --git a/src/Message/DPMResponse.php b/src/Message/DPMResponse.php
index 2a1f59c9..76298bb3 100644
--- a/src/Message/DPMResponse.php
+++ b/src/Message/DPMResponse.php
@@ -59,6 +59,9 @@ class DPMResponse extends AbstractResponse implements RedirectResponseInterface
         'x_email_customer',
 
         'x_delim_data',
+
+        // Custom omnipay field.
+        'omnipay_transaction_id',
     );
 
     /**