diff --git a/src/Traits/Follower.php b/src/Traits/Follower.php
index cf2cb4a..8c495c8 100644
--- a/src/Traits/Follower.php
+++ b/src/Traits/Follower.php
@@ -117,7 +117,7 @@ public function notApprovedFollowings(): HasMany
         return $this->followings()->notAccepted();
     }
 
-    public function attachFollowStatus($followables, callable $resolver = null)
+    public function attachFollowStatus($followables, ?callable $resolver = null)
     {
         $returnFirst = false;