diff --git a/src/Controller/Connect/RegisterController.php b/src/Controller/Connect/RegisterController.php
index f9e43f33e..7fb726421 100644
--- a/src/Controller/Connect/RegisterController.php
+++ b/src/Controller/Connect/RegisterController.php
@@ -56,7 +56,7 @@ public function __construct(
         FormFactoryInterface $formFactory,
         Environment $twig,
         string $grantRule,
-        string $registrationForm,
+        ?string $registrationForm,
         ?AccountConnectorInterface $accountConnector,
         ?RegistrationFormHandlerInterface $formHandler
     ) {