diff --git a/xcdat/spatial.py b/xcdat/spatial.py
index aec0b9a9..a16fd57a 100644
--- a/xcdat/spatial.py
+++ b/xcdat/spatial.py
@@ -8,6 +8,7 @@
     Hashable,
     List,
     Literal,
+    Optional,
     Tuple,
     TypedDict,
     Union,
@@ -263,7 +264,7 @@ def get_weights(
         and pressure).
         """
         Bounds = TypedDict(
-            "Bounds", {"weights_method": Callable, "region": np.ndarray | None}
+            "Bounds", {"weights_method": Callable, "region": Optional[np.ndarray]}
         )
 
         axis_bounds: Dict[SpatialAxis, Bounds] = {