diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
index b284823..3737b87 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
@@ -352,4 +352,25 @@ public function setLastModified($modified) {
     return $this;
   }
 
+  /**
+   * Provides a list of duplicate feeds.
+   *
+   * @return
+   *   An array with the list of duplicated feeds.
+   */
+  public function getFeedDuplicates() {
+    $query = \Drupal::entityQuery($this->entityTypeId);
+
+    $or_condition = $query->orConditionGroup()
+      ->condition('title', $this->label())
+      ->condition('url', $this->getUrl());
+    $query->condition($or_condition);
+
+    if ($this->id()) {
+      $query->condition('fid', $this->id(), '<>');
+    }
+
+    return \Drupal::entityManager()->getStorage($this->entityTypeId)->loadMultiple($query->execute());
+  }
+
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
index f5ec5f6..14ac73d 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
@@ -67,8 +67,7 @@ public function form(array $form, array &$form_state) {
   public function validate(array $form, array &$form_state) {
     $feed = $this->buildEntity($form, $form_state);
     // Check for duplicate titles.
-    $feed_storage = $this->entityManager->getStorage('aggregator_feed');
-    $result = $feed_storage->getFeedDuplicates($feed);
+    $result = $feed->getFeedDuplicates();
     foreach ($result as $item) {
       if (strcasecmp($item->label(), $feed->label()) == 0) {
         $this->setFormError('title', $form_state, $this->t('A feed named %feed already exists. Enter a unique title.', array('%feed' => $feed->label())));
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedInterface.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedInterface.php
index 29c6782..55362b1 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedInterface.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedInterface.php
@@ -240,4 +240,13 @@ public function deleteItems();
    */
   public function refreshItems();
 
+
+  /**
+   * Provides a list of duplicate feeds.
+   *
+   * @return
+   *   An array with the list of duplicated feeds.
+   */
+  public function getFeedDuplicates();
+
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorage.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorage.php
index 5824240..942abf5 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorage.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorage.php
@@ -21,24 +21,6 @@ class FeedStorage extends ContentEntityDatabaseStorage implements FeedStorageInt
   /**
    * {@inheritdoc}
    */
-  public function getFeedDuplicates(FeedInterface $feed) {
-    $query = \Drupal::entityQuery('aggregator_feed');
-
-    $or_condition = $query->orConditionGroup()
-      ->condition('title', $feed->label())
-      ->condition('url', $feed->getUrl());
-    $query->condition($or_condition);
-
-    if ($feed->id()) {
-      $query->condition('fid', $feed->id(), '<>');
-    }
-
-    return $this->loadMultiple($query->execute());
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function getFeedIdsToRefresh() {
     return $this->database->query('SELECT fid FROM {aggregator_feed} WHERE queued = 0 AND checked + refresh < :time AND refresh <> :never', array(
       ':time' => REQUEST_TIME,
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageInterface.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageInterface.php
index 2746b69..8c2fca7 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageInterface.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageInterface.php
@@ -16,17 +16,6 @@
 interface FeedStorageInterface extends EntityStorageInterface {
 
   /**
-   * Provides a list of duplicate feeds.
-   *
-   * @param \Drupal\aggregator\Entity\FeedInterface $feed
-   *   The feed entity.
-   *
-   * @return
-   *   An array with the list of duplicated feeds.
-   */
-  public function getFeedDuplicates(FeedInterface $feed);
-
-  /**
    * Returns the fids of feeds that need to be refreshed.
    *
    *  @return array