diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index 1b71245..0b5df66 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -383,8 +383,8 @@ function forum_node_update(EntityInterface $node) {
       }
       $query->execute();
       // The logic for determining last_comment_count is fairly complex, so
-      // call _forum_update_forum_index() too.
-      _forum_update_forum_index($node->id());
+      // call update the index too.
+      Drupal::service('forum_manager')->updateIndex($node->id());
     }
     // When a forum node is unpublished, remove it from the forum_index table.
     else {