diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index d6116f75513f..141627c69a76 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -259,6 +259,7 @@ dev2udev(dev_t x)
 dev_t
 udev2dev(udev_t x, int b)
 {
+	static int whine;
 
 	if (x == NOUDEV)
 		return (NODEV);
@@ -266,6 +267,10 @@ udev2dev(udev_t x, int b)
 		case 0:
 			return makedev(umajor(x), uminor(x));
 		case 1:
+			if (!whine) {
+				printf("WARNING: run /dev/MAKEDEV to get rid of block devices before 2000-06-01\n");
+				whine++;
+			}
 			return makebdev(umajor(x), uminor(x));
 		default:
 			Debugger("udev2dev(...,X)");