diff --git a/kitty/boss.py b/kitty/boss.py
index a15185b0e..40b6caf0e 100644
--- a/kitty/boss.py
+++ b/kitty/boss.py
@@ -364,7 +364,7 @@ class Boss(Thread):
 
     @callback
     def on_mouse_move(self, window, xpos, ypos):
-        mouse_cursor_pos[:2] = int(xpos * viewport_size.x_ratio), int(ypos * viewport_size.y_ratio)
+        mouse_cursor_pos[:2] = xpos, ypos = int(xpos * viewport_size.x_ratio), int(ypos * viewport_size.y_ratio)
         self.show_mouse_cursor()
         w = self.window_for_pos(xpos, ypos)
         if w is not None: