diff --git a/src/Plugin/Block/ShortenBlock.php b/src/Plugin/Block/ShortenBlock.php
index ff29b1c..dad3361 100644
--- a/src/Plugin/Block/ShortenBlock.php
+++ b/src/Plugin/Block/ShortenBlock.php
@@ -6,6 +6,7 @@
 
 namespace Drupal\shorten\Plugin\Block;
 
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Block\BlockBase;
 use Drupal\Core\Form\FormBuilderInterface;
@@ -20,7 +21,7 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
  *   category = @Translation("Forms")
  * )
  */
-class ShortenBlock extends BlockBase {
+class ShortenBlock extends BlockBase implements ContainerFactoryPluginInterface {
 
   /**
    * The form builder.