diff --git a/src/Xrandr.c b/src/Xrandr.c
index b1e97ec..85d30bc 100644
--- a/src/Xrandr.c
+++ b/src/Xrandr.c
@@ -483,6 +483,11 @@ int XRRUpdateConfiguration(XEvent *event)
 	scevent = (XRRScreenChangeNotifyEvent *) event;
 	snum = XRRRootToScreen(dpy,
 			       ((XRRScreenChangeNotifyEvent *) event)->root);
+	/* check for return value, fails on nx.
+	   https://bugs.launchpad.net/ubuntu-advantage/+bug/1084793*/
+	if (snum == -1 ) {
+		return 0;
+	}
 	if (scevent->rotation & (RR_Rotate_90 | RR_Rotate_270)) {
 		dpy->screens[snum].width   = scevent->height;
 		dpy->screens[snum].height  = scevent->width;