diff --git a/docs_src/body_nested_models/tutorial007.py b/docs_src/body_nested_models/tutorial007.py
index 9f321643c..dfbbeaab1 100644
--- a/docs_src/body_nested_models/tutorial007.py
+++ b/docs_src/body_nested_models/tutorial007.py
@@ -16,7 +16,7 @@ class Item(BaseModel):
     description: Optional[str] = None
     price: float
     tax: Optional[float] = None
-    tags: Set[str] = []
+    tags: Set[str] = set()
     images: Optional[List[Image]] = None