diff --git a/test/utils/stitching.py b/test/utils/stitching.py
index e9d435c..70a7076 100644
--- a/test/utils/stitching.py
+++ b/test/utils/stitching.py
@@ -58,7 +58,7 @@ class BoxSplitter:
         new_boxes = splitter(box)
         return new_boxes
 
-    def __tree_recurse(self, boxes, step):
+    def __tree_recurse(self, boxes, step)
         return map(rpartial(self.__split_recursively, step + 1), boxes)
 
     def __split_horizontal(self, box):
@@ -88,4 +88,4 @@ class BoxSplitter:
         box_left["c2"] = split_point
         box_right["c1"] = split_point
 
-        return box_left.box, box_right.box
\ No newline at end of file
+        return box_left.box, box_right.box