diff --git a/core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php b/core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
index ef6891c..dcafb77 100644
--- a/core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
+++ b/core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
@@ -183,7 +183,7 @@ public function processOutbound($path, &$options = array(), Request $request = N
         }
 
         // Add Drupal's subfolder from the base_path if there is one.
-        $options['base_url'] .= rtrim(base_path(), '/');
+        $options['base_url'] .= rtrim($request->getBaseUrl(), '/');
         if ($bubbleable_metadata) {
           $bubbleable_metadata->addCacheContexts(['languages:' . LanguageInterface::TYPE_URL, 'url.site']);
         }
diff --git a/core/modules/language/tests/src/Unit/LanguageNegotiationUrlTest.php b/core/modules/language/tests/src/Unit/LanguageNegotiationUrlTest.php
index 34abb61..f27dc81 100644
--- a/core/modules/language/tests/src/Unit/LanguageNegotiationUrlTest.php
+++ b/core/modules/language/tests/src/Unit/LanguageNegotiationUrlTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\Tests\language\Unit\LanguageNegotiationUrlTest.
  */
 
-namespace Drupal\Tests\language\Unit {
+namespace Drupal\Tests\language\Unit;
 
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Language\LanguageInterface;
@@ -255,14 +255,3 @@ public function providerTestDomain() {
     return $domain_configuration;
   }
 }
-
-}
-
-// @todo Remove as part of https://www.drupal.org/node/2481833.
-namespace {
-  if (!function_exists('base_path')) {
-    function base_path() {
-      return '/';
-    }
-  }
-}