https://bugs.freedesktop.org/show_bug.cgi?id=90320
--- Comment #7 from Nicolas Werner nicolas.werner@ymail.com --- N.Leiten seems to have found something, while looking into https://bugs.freedesktop.org/show_bug.cgi?id=73530 . As your problem seems to be rather similar, once there is a patch, the fix will hopefully also apply to you. Also there is some more information about what he found, maybe this can help you?