diff --git a/src/RedirectUriValidators/RedirectUriValidator.php b/src/RedirectUriValidators/RedirectUriValidator.php
index 4c61129fe..3e9e7abde 100644
--- a/src/RedirectUriValidators/RedirectUriValidator.php
+++ b/src/RedirectUriValidators/RedirectUriValidator.php
@@ -110,6 +110,6 @@ private function parseUrlAndRemovePort($url)
     {
         $uri = Uri::createFromString($url);
 
-        return (string) $uri->withPort(NULL);
+        return (string) $uri->withPort(null);
     }
 }