--- gdk/gdkevents.c	2014-12-03 20:05:41.835313686 +0100
+++ gdk/gdkevents.c.new	2014-12-03 20:01:25.235312446 +0100
@@ -1337,10 +1337,10 @@
     }
 
   if (delta_x)
-    *delta_x = dx;
+    *delta_x = dx * -1;
 
   if (delta_y)
-    *delta_y = dy;
+    *delta_y = dy * -1;
 
   return fetched;
 }