diff --git a/core/modules/forum/lib/Drupal/forum/ForumManager.php b/core/modules/forum/lib/Drupal/forum/ForumManager.php
index 81a631a..88c99d3 100644
--- a/core/modules/forum/lib/Drupal/forum/ForumManager.php
+++ b/core/modules/forum/lib/Drupal/forum/ForumManager.php
@@ -236,9 +236,9 @@ public function getTopics($tid) {
           $topic->new = 0;
         }
         else {
-          $history = $this->lastVisit($topic->nid);
+          $history = $this->lastVisit($topic->id());
           // @todo move use comment service.
-          $topic->new_replies = $this->numberNew($topic->nid, $history);
+          $topic->new_replies = $this->numberNew($topic->id(), $history);
           $topic->new = $topic->new_replies || ($topic->last_comment_timestamp > $history);
         }
       }
@@ -262,7 +262,7 @@ public function getTopics($tid) {
         $last_reply->uid = $topic->last_comment_uid;
         $topic->last_reply = $last_reply;
       }
-      $topics[$topic->nid] = $topic;
+      $topics[$topic->id()] = $topic;
     }
 
     return $topics;