--- lockdev-1.0.0/src/sample.c.jbj	2002-11-29 10:10:35.000000000 -0500
+++ lockdev-1.0.0/src/sample.c	2002-11-29 10:12:24.000000000 -0500
@@ -31,6 +31,8 @@
 		}
 		else dev = p;
 	}
+	if (dev == NULL)
+	    usage();
 	i = 0;
 	(void) dev_setpid(getppid());
 	switch(ch) {