diff --git a/core/modules/comment/comment.install b/core/modules/comment/comment.install
index 2e4d0a6..7112f6d 100644
--- a/core/modules/comment/comment.install
+++ b/core/modules/comment/comment.install
@@ -48,13 +48,13 @@ function comment_install() {
 function _comment_get_comment_fields() {
   $fields = entity_load_multiple_by_properties('field_entity', array(
     'type' => 'comment',
-    'include_inactive' => FALSE,
+    'include_inactive' => TRUE,
     'include_deleted' => FALSE,
   ));
   foreach ($fields as &$field) {
     $instances = entity_load_multiple_by_properties('field_instance', array(
       'field_uuid' => $field->uuid,
-      'include_inactive' => FALSE,
+      'include_inactive' => TRUE,
       'include_deleted' => FALSE,
     ));
     foreach ($instances as $instance) {
diff --git a/core/modules/comment/lib/Drupal/comment/CommentManager.php b/core/modules/comment/lib/Drupal/comment/CommentManager.php
index 3816fc4..fc833b8 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentManager.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentManager.php
@@ -56,12 +56,14 @@ public function getParentEntityUri(CommentInterface $comment) {
   /**
    * {@inheritdoc}
    */
-  public function getFields($entity_type = NULL) {
-    $map = $this->getAllFields();
-    if (!isset($map[$entity_type])) {
+  public function getFields($entity_type) {
+    $info = $this->entityManager->getDefinition($entity_type);
+    if (!is_subclass_of($info['class'], '\Drupal\Core\Entity\ContentEntityInterface')) {
       return array();
     }
-    return $map[$entity_type];
+
+    $map = $this->getAllFields();
+    return isset($map[$entity_type]) ? $map[$entity_type] : array();
   }
 
   /**
diff --git a/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php b/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
index 84a3589..1f091d9 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentManagerInterface.php
@@ -38,7 +38,7 @@ public function getParentEntityUri(CommentInterface $comment);
    *
    * @see field_info_field_map()
    */
-  public function getFields($entity_type = NULL);
+  public function getFields($entity_type);
 
   /**
    * Utility function to return all comment fields.