diff --git a/kivy/input/providers/mouse.py b/kivy/input/providers/mouse.py
index bb9c45da3..241db2e7d 100644
--- a/kivy/input/providers/mouse.py
+++ b/kivy/input/providers/mouse.py
@@ -206,10 +206,7 @@ class MouseMotionEventProvider(MotionEventProvider):
                 self.remove_touch(cur)
             self.current_drag = None
 
-        width, height = EventLoop.window.system_size
-        rx = x / float(width)
-        ry = 1. - y / float(height)
-        cur = self.find_touch(rx, ry)
+        cur = self.current_drag
         if (button in ('left', 'scrollup', 'scrolldown') or
                 self.disable_multitouch) and cur and not ('ctrl' in modifiers):
             self.remove_touch(cur)