diff --git a/core/lib/Drupal/Core/Routing/LocalAwareRedirectResponseTrait.php b/core/lib/Drupal/Core/Routing/LocalAwareRedirectResponseTrait.php
index 243af8a..0be5fb7 100644
--- a/core/lib/Drupal/Core/Routing/LocalAwareRedirectResponseTrait.php
+++ b/core/lib/Drupal/Core/Routing/LocalAwareRedirectResponseTrait.php
@@ -25,7 +25,7 @@
    * {@inheritdoc}
    */
   protected function isLocal($url) {
-    return !UrlHelper::isExternal($url) || UrlHelper::externalIsLocal($url, $this->getBaseUrl() . '/');
+    return !UrlHelper::isExternal($url) || UrlHelper::externalIsLocal($url, $this->getBaseUrl());
   }
 
   /**