diff --git a/core/modules/config_translation/src/Controller/ConfigTranslationController.php b/core/modules/config_translation/src/Controller/ConfigTranslationController.php
index 14213a0..fc10e7c 100644
--- a/core/modules/config_translation/src/Controller/ConfigTranslationController.php
+++ b/core/modules/config_translation/src/Controller/ConfigTranslationController.php
@@ -13,6 +13,7 @@
 use Drupal\Core\Access\AccessManagerInterface;
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\Language\Language;
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\Core\PathProcessor\InboundPathProcessorInterface;
 use Drupal\Core\Render\RendererInterface;
@@ -166,7 +167,7 @@ public function itemPage(Request $request, RouteMatchInterface $route_match, $pl
       ];
       drupal_set_message($this->renderer->renderPlain($message), 'warning');
 
-      $original_langcode = 'und';
+      $original_langcode = LanguageInterface::LANGCODE_NOT_SPECIFIED;
       $operations_access = FALSE;
     }