diff --git a/sys/dev/raid/vinum/vinumconfig.c b/sys/dev/raid/vinum/vinumconfig.c
--- a/sys/dev/raid/vinum/vinumconfig.c
+++ b/sys/dev/raid/vinum/vinumconfig.c
@@ -1728,7 +1728,7 @@
     struct drive *drive = &DRIVE[driveno];
     int sdno;
 
-    if ((driveno > vinum_conf.drives_allocated)		    /* not a valid drive */
+    if ((driveno >= vinum_conf.drives_allocated)		    /* not a valid drive */
     ||(drive->state == drive_unallocated)) {		    /* or nothing there */
 	ioctl_reply->error = EINVAL;
 	strcpy(ioctl_reply->msg, "No such drive");