diff --git a/webht/third_party/pay/controllers/iPayLinksService.php b/webht/third_party/pay/controllers/iPayLinksService.php
index 559ded7d..9a36a765 100644
--- a/webht/third_party/pay/controllers/iPayLinksService.php
+++ b/webht/third_party/pay/controllers/iPayLinksService.php
@@ -687,7 +687,7 @@ class IPayLinksService extends CI_Controller
             $ret->data = $respObject = (Object) $resp;
             $ref = "";
         } else {
-            $ref = $_SERVER['HTTP_REFERER'];
+            $ref = $_SERVER['HTTP_REFERER'] ? $_SERVER['HTTP_REFERER'] : NULL;
             $r = iconv("UTF-8", "UTF-8//IGNORE", $resp);
             $ret->data = $respObject = @ simplexml_load_string($resp);
             // test