diff -u b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
--- b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
+++ b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
@@ -15,7 +15,7 @@
 use Drupal\Core\Entity\Query\QueryInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
-use Drupal\Core\Render\Renderer;
+use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Session\AccountInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -52,9 +52,9 @@
   protected $itemQuery;
 
   /**
-   * Rendering service.
+   * The renderer service.
    *
-   * @var \Drupal\Core\Render\Renderer
+   * @var \Drupal\Core\Render\RendererInterface
    */
   protected $renderer;
 
@@ -73,10 +73,10 @@
    *   The entity storage for feed items.
    * @param \Drupal\Core\Entity\Query\QueryInterface $item_query
    *   The entity query object for feed items.
-   * @param \Drupal\Core\Render\Renderer $renderer
+   * @param \Drupal\Core\Render\RendererInterface $renderer
    *   The renderer service.
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, FeedStorageInterface $feed_storage, ItemStorageInterface $item_storage, QueryInterface $item_query, Renderer $renderer) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, FeedStorageInterface $feed_storage, ItemStorageInterface $item_storage, QueryInterface $item_query, RendererInterface $renderer) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
     $this->feedStorage = $feed_storage;
     $this->itemStorage = $item_storage;