diff --git a/core/lib/Drupal/Core/Access/AccessManager.php b/core/lib/Drupal/Core/Access/AccessManager.php
index 89e9268..2dfd3e7 100644
--- a/core/lib/Drupal/Core/Access/AccessManager.php
+++ b/core/lib/Drupal/Core/Access/AccessManager.php
@@ -200,7 +200,7 @@ public function checkNamedRoute($route_name, array $parameters = array(), Accoun
       if (empty($route_request)) {
         // Create a request and copy the account from the current request.
         $route_request = RequestHelper::duplicate($this->request, $this->urlGenerator->generate($route_name, $parameters));
-        $defaults = $parameters;
+        $defaults = $route->getDefaults() + $parameters;
         $defaults[RouteObjectInterface::ROUTE_OBJECT] = $route;
         $route_request->attributes->add($this->paramConverterManager->enhance($defaults, $route_request));
       }