--- ../clean/asterisk-1.4.15/main/devicestate.c	2007-06-06 14:20:27.000000000 +0200
+++ main/devicestate.c	2007-12-16 19:45:24.000000000 +0200
@@ -330,8 +330,11 @@
 int ast_device_state_changed_literal(const char *dev)
 {
 	char *buf;
-	buf = ast_strdupa(dev);
-	return __ast_device_state_changed_literal(buf);
+	if (dev) {
+		buf = ast_strdupa(dev);
+		return __ast_device_state_changed_literal(buf);
+	} else
+		return -1;
 }
 
 /*! \brief Accept change notification, add it to change queue */