diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageController.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageController.php
index 1ff529f..69bf8c3 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageController.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageController.php
@@ -8,7 +8,7 @@
 namespace Drupal\aggregator;
 
 use Drupal\Core\Entity\DatabaseStorageControllerNG;
-use Drupal\Core\Entity\EntityInterface;
+use Drupal\aggregator\Entity\FeedInterface;
 
 /**
  * Controller class for aggregator's feeds.
@@ -38,7 +38,7 @@ public function loadCategories(array $feeds) {
   /**
    * {@inheritdoc}
    */
-  public function saveCategories(EntityInterface $feed, array $categories) {
+  public function saveCategories(FeedInterface $feed, array $categories) {
     foreach ($categories as $cid => $value) {
       if ($value) {
         $this->database->insert('aggregator_category_feed')
@@ -72,7 +72,7 @@ public function getFeedDuplicates(EntityInterface $feed) {
       $query = $this->database->query("SELECT title, url FROM {aggregator_feed} WHERE title = :title OR url = :url", array(':title' => $feed->label(), ':url' => $feed->url->value));
     }
 
-    return $query;
+    return $query->fetchAll();
   }
 
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageControllerInterface.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageControllerInterface.php
index cd8162c..9ca3e24 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageControllerInterface.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedStorageControllerInterface.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\aggregator;
 
-use Drupal\Core\Entity\EntityInterface;
+use Drupal\aggregator\Entity\FeedInterface;
 use Drupal\Core\Entity\EntityStorageControllerInterface;
 
 /**
@@ -27,12 +27,12 @@ public function loadCategories(array $feeds);
   /**
    * Saves the categories of a feed.
    *
-   * @param \Drupal\Core\Entity\EntityInterface $feed
+   * @param \Drupal\aggregator\Entity\FeedInterface $feed
    *   The feed entity.
    * @param array $categories
    *   The array of categories.
    */
-  public function saveCategories(EntityInterface $feed, array $categories);
+  public function saveCategories(FeedInterface $feed, array $categories);
 
   /**
    * Deletes the categories of a feed.
@@ -47,6 +47,9 @@ public function deleteCategories(array $feeds);
    *
    * @param \Drupal\Core\Entity\EntityInterface $feed
    *   The feed entity.
+   *
+   * @return
+   *   An array with the list of duplicated feeds.
    */
-  public function getFeedDuplicates(EntityInterface $feed);
+  public function getFeedDuplicates(FeedInterface $feed);
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Form/OpmlFeedAdd.php b/core/modules/aggregator/lib/Drupal/aggregator/Form/OpmlFeedAdd.php
index 8eee427..a157946 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Form/OpmlFeedAdd.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Form/OpmlFeedAdd.php
@@ -10,7 +10,6 @@
 use Drupal\aggregator\CategoryStorageControllerInterface;
 use Drupal\aggregator\FeedStorageControllerInterface;
 use Drupal\Component\Utility\Url;
-use Drupal\Core\Database\Connection;
 use Drupal\Core\Entity\Query\QueryFactory;
 use Drupal\Core\Form\FormBase;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -24,13 +23,6 @@
 class OpmlFeedAdd extends FormBase {
 
   /**
-   * The database connection object.
-   *
-   * @var \Drupal\Core\Database\Connection
-   */
-  protected $database;
-
-  /**
    * The entity query factory object.
    *
    * @var \Drupal\Core\Entity\Query\QueryFactory
@@ -61,8 +53,6 @@ class OpmlFeedAdd extends FormBase {
   /**
    * Constructs a database object.
    *
-   * @param \Drupal\Core\Database\Connection $database
-   *   The database object.
    * @param \Drupal\Core\Entity\Query\QueryFactory $query_factory
    *   The entity query object.
    * @param \Drupal\aggregator\FeedStorageControllerInterface $feed_storage
@@ -72,8 +62,7 @@ class OpmlFeedAdd extends FormBase {
    * @param \Drupal\aggregator\CategoryStorageControllerInterface $category_storage_controller
    *   The category storage controller.
    */
-  public function __construct(Connection $database, QueryFactory $query_factory, FeedStorageControllerInterface $feed_storage, ClientInterface $http_client, CategoryStorageControllerInterface $category_storage_controller) {
-    $this->database = $database;
+  public function __construct(QueryFactory $query_factory, FeedStorageControllerInterface $feed_storage, ClientInterface $http_client, CategoryStorageControllerInterface $category_storage_controller) {
     $this->queryFactory = $query_factory;
     $this->feedStorage = $feed_storage;
     $this->httpClient = $http_client;
@@ -85,7 +74,6 @@ public function __construct(Connection $database, QueryFactory $query_factory, F
    */
   public static function create(ContainerInterface $container) {
     return new static(
-      $container->get('database'),
       $container->get('entity.query'),
       $container->get('entity.manager')->getStorageController('aggregator_feed'),
       $container->get('http_default_client'),