diff --git a/test/utils/stitching.py b/test/utils/stitching.py
index bb4aca9..06b406a 100644
--- a/test/utils/stitching.py
+++ b/test/utils/stitching.py
@@ -75,8 +75,8 @@ class BoxSplitter:
         )
 
     @staticmethod
-    def __large_enough(box):
-        return box["dim"] >= 10
+    def __large_enough(wrapped_box: SplitKeyMapper):
+        return wrapped_box["dim"] >= 10
 
     @staticmethod
     def __get_child_boxes(wrapped_box: SplitKeyMapper):