diff --git a/MangoPay/PayOutPaymentRef.php b/MangoPay/PayOutPaymentRef.php
index 6d6a5d95..d903ee9c 100644
--- a/MangoPay/PayOutPaymentRef.php
+++ b/MangoPay/PayOutPaymentRef.php
@@ -13,5 +13,5 @@ class PayOutPaymentRef extends Libraries\Dto
     /**
      * @var string
      */
-    public $referenceId;
+    public $ReferenceId;
 }
\ No newline at end of file