diff --git a/src/sugar3/graphics/palettewindow.py b/src/sugar3/graphics/palettewindow.py
index 13684faf..3ea5f017 100644
--- a/src/sugar3/graphics/palettewindow.py
+++ b/src/sugar3/graphics/palettewindow.py
@@ -441,6 +441,7 @@ class MouseSpeedDetector(GObject.GObject):
     def stop(self):
         if self._timeout_hid is not None:
             GObject.source_remove(self._timeout_hid)
+            self._timeout_hid = None
         self._state = None
 
     def _get_mouse_position(self):