diff --git a/src/Models/Concerns/KeepsDeletedModels.php b/src/Models/Concerns/KeepsDeletedModels.php
index 6b53938..3c8f793 100644
--- a/src/Models/Concerns/KeepsDeletedModels.php
+++ b/src/Models/Concerns/KeepsDeletedModels.php
@@ -65,7 +65,7 @@ public static function deletedModels(): Builder
         return static::getDeletedModelClassName()::query()->where('model', $model);
     }
 
-    public static function restore(mixed $key, Closure $beforeSaving = null): Model
+    public static function restore(mixed $key, ?Closure $beforeSaving = null): Model
     {
         $deletedModel = self::findDeletedModelToRestore($key);