diff --git a/extensions/approval/src/Listener/UnapproveNewContent.php b/extensions/approval/src/Listener/UnapproveNewContent.php
index 8f95dd951..bbd3bcb31 100644
--- a/extensions/approval/src/Listener/UnapproveNewContent.php
+++ b/extensions/approval/src/Listener/UnapproveNewContent.php
@@ -24,7 +24,7 @@ class UnapproveNewContent
         $post = $event->post;
 
         if (! $post->exists) {
-            $ability = $post->discussion->post_number_index == 0 ? 'startWithoutApproval' : 'replyWithoutApproval';
+            $ability = $post->discussion->first_post_id === null ? 'startWithoutApproval' : 'replyWithoutApproval';
 
             if ($event->actor->can($ability, $post->discussion)) {
                 if ($post->is_approved === null) {
diff --git a/framework/core/src/Discussion/Discussion.php b/framework/core/src/Discussion/Discussion.php
index db96639ef..544b7f042 100644
--- a/framework/core/src/Discussion/Discussion.php
+++ b/framework/core/src/Discussion/Discussion.php
@@ -30,7 +30,7 @@ use Illuminate\Support\Str;
  * @property string $slug
  * @property int $comment_count
  * @property int $participant_count
- * @property int $post_number_index
+ * @property int $post_number_index !!DEPRECATED!!
  * @property \Carbon\Carbon $created_at
  * @property int|null $user_id
  * @property int|null $first_post_id
diff --git a/framework/core/src/Post/Command/PostReplyHandler.php b/framework/core/src/Post/Command/PostReplyHandler.php
index 40a52de7f..96de698d0 100644
--- a/framework/core/src/Post/Command/PostReplyHandler.php
+++ b/framework/core/src/Post/Command/PostReplyHandler.php
@@ -74,7 +74,7 @@ class PostReplyHandler
 
         // If this is the first post in the discussion, it's technically not a
         // "reply", so we won't check for that permission.
-        if ($discussion->post_number_index > 0) {
+        if ($discussion->first_post_id !== null) {
             $actor->assertCan('reply', $discussion);
         }