diff --git a/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php b/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
index f964ff27c61..36436037e75 100755
--- a/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
+++ b/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
@@ -201,9 +201,8 @@ protected function getKeys(array $models, $key = null)
         $castKeyToString = in_array(SchemaBuilder::$defaultMorphKeyType, ['uuid', 'ulid', 'string']);
 
         return (new Collection(parent::getKeys($models, $key)))
-            ->transform(function ($key) use ($castKeyToString) {
-                return $castKeyToString === true ? (string) $key : $key;
-            })->all();
+            ->transform(fn ($key) => $castKeyToString === true ? (string) $key : $key)
+            ->all();
     }
 
     /** @inheritDoc */