diff -u b/core/lib/Drupal/Core/Block/BlockBase.php b/core/lib/Drupal/Core/Block/BlockBase.php
--- b/core/lib/Drupal/Core/Block/BlockBase.php
+++ b/core/lib/Drupal/Core/Block/BlockBase.php
@@ -18,7 +18,7 @@
 use Drupal\Core\Plugin\ContextAwarePluginBase;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Component\Utility\NestedArray;
-use Drupal\Core\Language\Language;
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Component\Transliteration\TransliterationInterface;
@@ -415,7 +415,7 @@
     // @todo This is basically the same as what is done in
     //   \Drupal\system\MachineNameController::transliterate(), so it might make
     //   sense to provide a common service for the two.
-    $transliterated = $this->transliteration()->transliterate($admin_label, Language::LANGCODE_DEFAULT, '_');
+    $transliterated = $this->transliteration()->transliterate($admin_label, LanguageInterface::LANGCODE_DEFAULT, '_');
 
     $replace_pattern = '[^a-z0-9_.]+';
 
@@ -563,2 +563,3 @@
   }
+
 }