--- a/dwm.c	Mon Aug 18 19:28:57 2008 +0100
+++ b/dwm.c	Fri Aug 22 15:26:30 2008 +0200
@@ -1469,8 +1469,12 @@
 
 void
 toggletag(const Arg *arg) {
-	unsigned int mask = sel->tags ^ (arg->ui & TAGMASK);
+	unsigned int mask;
 
+	if (!sel)
+		return;
+	
+	mask = sel->tags ^ (arg->ui & TAGMASK);
 	if(sel && mask) {
 		sel->tags = mask;
 		arrange();