diff --git a/ninja/operation.py b/ninja/operation.py
index a63fb8ee..455a1668 100644
--- a/ninja/operation.py
+++ b/ninja/operation.py
@@ -60,7 +60,7 @@ def __init__(
         self.path: str = path
         self.methods: List[str] = methods
         self.view_func: Callable = view_func
-        self.api: "NinjaAPI" = cast("NinjaAPI", None)
+        self.api: NinjaAPI = cast("NinjaAPI", None)
         if url_name is not None:
             self.url_name = url_name
 
diff --git a/ninja/router.py b/ninja/router.py
index 13e26d41..f471e80b 100644
--- a/ninja/router.py
+++ b/ninja/router.py
@@ -36,7 +36,7 @@ def __init__(
         throttle: Union[BaseThrottle, List[BaseThrottle], NOT_SET_TYPE] = NOT_SET,
         tags: Optional[List[str]] = None,
     ) -> None:
-        self.api: Optional["NinjaAPI"] = None
+        self.api: Optional[NinjaAPI] = None
         self.auth = auth
         self.throttle = throttle
         self.tags = tags