diff --git a/core/modules/comment/lib/Drupal/comment/CommentManager.php b/core/modules/comment/lib/Drupal/comment/CommentManager.php
index 7548839..2f64cac 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentManager.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentManager.php
@@ -13,6 +13,7 @@
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\Query\QueryFactory;
+use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Routing\UrlGeneratorInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\StringTranslation\TranslationInterface;
@@ -80,6 +81,13 @@ class CommentManager implements CommentManagerInterface {
   protected $urlGenerator;
 
   /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
    * Construct the CommentManager object.
    *
    * @param \Drupal\field\FieldInfo $field_info
@@ -96,8 +104,10 @@ class CommentManager implements CommentManagerInterface {
    *   The string translation service.
    * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
    *   The url generator service.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
    */
-  public function __construct(FieldInfo $field_info, EntityManagerInterface $entity_manager, QueryFactory $query_factory, AccountInterface $current_user, ConfigFactoryInterface $config_factory, TranslationInterface $translation_manager, UrlGeneratorInterface $url_generator) {
+  public function __construct(FieldInfo $field_info, EntityManagerInterface $entity_manager, QueryFactory $query_factory, AccountInterface $current_user, ConfigFactoryInterface $config_factory, TranslationInterface $translation_manager, UrlGeneratorInterface $url_generator, ModuleHandlerInterface $module_handler) {
     $this->fieldInfo = $field_info;
     $this->entityManager = $entity_manager;
     $this->queryFactory = $query_factory;
@@ -105,6 +115,7 @@ public function __construct(FieldInfo $field_info, EntityManagerInterface $entit
     $this->userConfig = $config_factory->get('user.settings');
     $this->translationManager = $translation_manager;
     $this->urlGenerator = $url_generator;
+    $this->moduleHandler = $module_handler;
   }
 
   /**
@@ -332,7 +343,7 @@ public function forbiddenMessage(EntityInterface $entity, $field_name) {
   public function getCountNewComments(EntityInterface $entity, $field_name = NULL, $timestamp = 0) {
     // @todo Replace module handler with optional history service injection
     //   after http://drupal.org/node/2081585
-    if ($this->currentUser->isAuthenticated() && \Drupal::moduleHandler()->moduleExists('history')) {
+    if ($this->currentUser->isAuthenticated() && $this->moduleHandler->moduleExists('history')) {
       // Retrieve the timestamp at which the current user last viewed this entity.
       if (!$timestamp) {
         if ($entity->getEntityTypeId() == 'node') {
diff --git a/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php b/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
index c83f5ae..61c35f5 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
@@ -8,8 +8,6 @@
 namespace Drupal\comment;
 
 use Drupal\Core\Entity\EntityInterface;
-use Drupal\Core\Session\AccountInterface;
-
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 
 /**
diff --git a/core/modules/forum/tests/Drupal/forum/Tests/ForumManagerTest.php b/core/modules/forum/tests/Drupal/forum/Tests/ForumManagerTest.php
index ee52b0a..9429592 100644
--- a/core/modules/forum/tests/Drupal/forum/Tests/ForumManagerTest.php
+++ b/core/modules/forum/tests/Drupal/forum/Tests/ForumManagerTest.php
@@ -74,7 +74,7 @@ public function testGetIndex() {
       ->disableOriginalConstructor()
       ->getMock();
 
-    $comment_manager = $this->getMockBuilder('\Drupal\comment\CommentManager')
+    $comment_manager = $this->getMockBuilder('\Drupal\comment\CommentManagerInterface')
       ->disableOriginalConstructor()
       ->getMock();