diff --git a/colcon_notification/desktop_notification/win32.py b/colcon_notification/desktop_notification/win32.py
index 9c8af54..82395ec 100644
--- a/colcon_notification/desktop_notification/win32.py
+++ b/colcon_notification/desktop_notification/win32.py
@@ -124,3 +124,5 @@ def _on_destroy(hwnd, msg, wparam, lparam):  # noqa: D102
                 'Failed to delete the notification handle: {e}'
                 .format_map(locals()))
         win32gui.PostQuitMessage(0)
+
+        return 0