diff --git a/wxPython/demo/ShapedWindow.py b/wxPython/demo/ShapedWindow.py
index de364e638e..ea8f7b8b7d 100644
--- a/wxPython/demo/ShapedWindow.py
+++ b/wxPython/demo/ShapedWindow.py
@@ -35,6 +35,7 @@ class TestFrame(wxFrame):
 
 
     def SetWindowShape(self, *evt):
+        # Use the bitmap's mask to determine the region
         r = wxRegionFromBitmap(self.bmp)
         self.hasShape = self.SetShape(r)