diff --git a/app/queries/optional_item_query.rb b/app/queries/optional_item_query.rb
index 54cd0eed0..ea3bca043 100644
--- a/app/queries/optional_item_query.rb
+++ b/app/queries/optional_item_query.rb
@@ -28,8 +28,8 @@ class OptionalItemQuery < ApplicationQuery
     items = items.where(public: public)
 
     # 难度
-    difficulty = difficulty ? difficulty.to_i : 1
-    items = items.where(difficulty: difficulty)
+    diff = difficulty ? difficulty.to_i : 1
+    items = items.where(difficulty: diff)
     items
   end
 end
\ No newline at end of file