diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
index ba7c846..6bfe43a 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
@@ -40,6 +40,13 @@
 class Feed extends ContentEntityBase implements FeedInterface {
 
   /**
+   * @todo Remove this or document it.
+   *
+   * @var array
+   */
+  public $items;
+
+  /**
    * Implements Drupal\Core\Entity\EntityInterface::id().
    */
   public function id() {