diff --git a/extensions/approval/extend.php b/extensions/approval/extend.php
index 0f1417539..5140b6756 100644
--- a/extensions/approval/extend.php
+++ b/extensions/approval/extend.php
@@ -7,6 +7,8 @@
  * LICENSE file that was distributed with this source code.
  */
 
+use Flarum\Api\Serializer\BasicDiscussionSerializer;
+use Flarum\Api\Serializer\PostSerializer;
 use Flarum\Approval\Access;
 use Flarum\Approval\Listener;
 use Flarum\Discussion\Discussion;
@@ -30,10 +32,21 @@ return [
     (new Extend\Model(Post::class))
         ->default('is_approved', true),
 
+    (new Extend\ApiSerializer(BasicDiscussionSerializer::class))
+        ->attribute('isApproved', function ($serializer, Discussion $discussion) {
+            return (bool) $discussion->is_approved;
+        }),
+
+    (new Extend\ApiSerializer(PostSerializer::class))
+        ->attribute('isApproved', function ($serializer, Post $post) {
+            return (bool) $post->is_approved;
+        })->attribute('canApprove', function (PostSerializer $serializer, Post $post) {
+            return (bool) $serializer->getActor()->can('approvePosts', $post->discussion);
+        }),
+
     new Extend\Locales(__DIR__.'/locale'),
 
     function (Dispatcher $events) {
-        $events->subscribe(Listener\AddPostApprovalAttributes::class);
         $events->subscribe(Listener\ApproveContent::class);
         $events->subscribe(Listener\UnapproveNewContent::class);
 
diff --git a/extensions/approval/src/Listener/AddPostApprovalAttributes.php b/extensions/approval/src/Listener/AddPostApprovalAttributes.php
deleted file mode 100644
index d2fe96e6a..000000000
--- a/extensions/approval/src/Listener/AddPostApprovalAttributes.php
+++ /dev/null
@@ -1,41 +0,0 @@
-<?php
-
-/*
- * This file is part of Flarum.
- *
- * For detailed copyright and license information, please view the
- * LICENSE file that was distributed with this source code.
- */
-
-namespace Flarum\Approval\Listener;
-
-use Flarum\Api\Event\Serializing;
-use Flarum\Api\Serializer\BasicDiscussionSerializer;
-use Flarum\Api\Serializer\PostSerializer;
-use Illuminate\Contracts\Events\Dispatcher;
-
-class AddPostApprovalAttributes
-{
-    /**
-     * @param Dispatcher $events
-     */
-    public function subscribe(Dispatcher $events)
-    {
-        $events->listen(Serializing::class, [$this, 'addApiAttributes']);
-    }
-
-    /**
-     * @param Serializing $event
-     */
-    public function addApiAttributes(Serializing $event)
-    {
-        if ($event->isSerializer(BasicDiscussionSerializer::class)
-            || $event->isSerializer(PostSerializer::class)) {
-            $event->attributes['isApproved'] = (bool) $event->model->is_approved;
-        }
-
-        if ($event->isSerializer(PostSerializer::class)) {
-            $event->attributes['canApprove'] = (bool) $event->actor->can('approvePosts', $event->model->discussion);
-        }
-    }
-}