diff --git a/great_expectations/expectations/expectation.py b/great_expectations/expectations/expectation.py
index 394778b5513a..2e3a7d69346b 100644
--- a/great_expectations/expectations/expectation.py
+++ b/great_expectations/expectations/expectation.py
@@ -332,7 +332,7 @@ def schema_extra(schema: Dict[str, Any], model: Type[Expectation]) -> None:
     args_keys: ClassVar[Tuple[str, ...]] = ()
 
     expectation_type: ClassVar[str]
-    windows: Optional[List[Window]] = pydantic.Field(default=None, description=WINDOWS_DESCRIPTION)
+    windows: Optional[List[Window]] = pydantic.Field(description=WINDOWS_DESCRIPTION)
     examples: ClassVar[List[dict]] = []
 
     _save_callback: Union[Callable[[Expectation], Expectation], None] = pydantic.PrivateAttr(