diff --git a/modules/paypal/express_checkout/payment.php b/modules/paypal/express_checkout/payment.php
index c9a6ecd5..20185209 100755
--- a/modules/paypal/express_checkout/payment.php
+++ b/modules/paypal/express_checkout/payment.php
@@ -178,7 +178,7 @@ if ($request_type && $ppec->type) {
 
 	// @ANTADIS - if id_billing make transaction
 	if ($id_billing_to_use != 0) {
-		if(!$ppec->DoReferenceTransaction($id_billing_to_use)){
+		if($ppec->DoReferenceTransaction($id_billing_to_use) === false){
 			return Tools::redirectLink($ppec->context->link->getPageLink('order.php').'?step=3&cgv=1&paypal_error=1');
 		}
 		$amount_match = $ppec->rightPaymentProcess();