diff --git a/extensions/lock/extend.php b/extensions/lock/extend.php
index 1413ffa47..0e7b55cd5 100644
--- a/extensions/lock/extend.php
+++ b/extensions/lock/extend.php
@@ -7,11 +7,11 @@
  * LICENSE file that was distributed with this source code.
  */
 
-use Flarum\Api\Event\Serializing;
 use Flarum\Api\Serializer\BasicDiscussionSerializer;
+use Flarum\Api\Serializer\DiscussionSerializer;
+use Flarum\Discussion\Discussion;
 use Flarum\Discussion\Event\Saving;
 use Flarum\Event\ConfigureDiscussionGambits;
-use Flarum\Event\ConfigurePostTypes;
 use Flarum\Extend;
 use Flarum\Lock\Access;
 use Flarum\Lock\Event\DiscussionWasLocked;
@@ -35,19 +35,26 @@ return [
     (new Extend\Notification())
         ->type(DiscussionLockedBlueprint::class, BasicDiscussionSerializer::class, ['alert']),
 
-    function (Dispatcher $events) {
-        $events->listen(ConfigureDiscussionGambits::class, function (ConfigureDiscussionGambits $event) {
+    (new Extend\ApiSerializer(DiscussionSerializer::class))
+        ->attribute('isLocked', function (DiscussionSerializer $serializer, Discussion $discussion) {
+            return (bool) $discussion->is_locked;
+        })
+        ->attribute('canLock', function (DiscussionSerializer $serializer, Discussion $discussion) {
+            return (bool) $serializer->getActor()->can('lock', $discussion);
+        }),
+
+    (new Extend\Post())
+        ->type(DiscussionLockedPost::class),
+
+    (new Extend\Event())
+        ->listen(ConfigureDiscussionGambits::class, function (ConfigureDiscussionGambits $event) {
             $event->gambits->add(LockedGambit::class);
-        });
-        $events->listen(Serializing::class, Listener\AddDiscussionLockedAttributes::class);
-        $events->listen(Saving::class, Listener\SaveLockedToDatabase::class);
-
-        $events->listen(ConfigurePostTypes::class, function (ConfigurePostTypes $event) {
-            $event->add(DiscussionLockedPost::class);
-        });
-        $events->listen(DiscussionWasLocked::class, Listener\CreatePostWhenDiscussionIsLocked::class);
-        $events->listen(DiscussionWasUnlocked::class, Listener\CreatePostWhenDiscussionIsUnlocked::class);
+        })
+        ->listen(Saving::class, Listener\SaveLockedToDatabase::class)
+        ->listen(DiscussionWasLocked::class, Listener\CreatePostWhenDiscussionIsLocked::class)
+        ->listen(DiscussionWasUnlocked::class, Listener\CreatePostWhenDiscussionIsUnlocked::class),
 
+    function (Dispatcher $events) {
         $events->subscribe(Access\DiscussionPolicy::class);
     },
 ];
diff --git a/extensions/lock/src/Listener/AddDiscussionLockedAttributes.php b/extensions/lock/src/Listener/AddDiscussionLockedAttributes.php
deleted file mode 100755
index 551cabe3f..000000000
--- a/extensions/lock/src/Listener/AddDiscussionLockedAttributes.php
+++ /dev/null
@@ -1,24 +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\Lock\Listener;
-
-use Flarum\Api\Event\Serializing;
-use Flarum\Api\Serializer\DiscussionSerializer;
-
-class AddDiscussionLockedAttributes
-{
-    public function handle(Serializing $event)
-    {
-        if ($event->isSerializer(DiscussionSerializer::class)) {
-            $event->attributes['isLocked'] = (bool) $event->model->is_locked;
-            $event->attributes['canLock'] = (bool) $event->actor->can('lock', $event->model);
-        }
-    }
-}