diff -u b/core/lib/Drupal/Component/Utility/LRUArrayObject.php b/core/lib/Drupal/Component/Utility/LRUArrayObject.php
--- b/core/lib/Drupal/Component/Utility/LRUArrayObject.php
+++ b/core/lib/Drupal/Component/Utility/LRUArrayObject.php
@@ -1,5 +1,10 @@
 <?php
 
+/**
+ * @file
+ * Definition of Drupal\Component\Utility\LRUArrayObject.
+ */
+
 namespace Drupal\Component\Utility;
 use ArrayObject;