diff --git a/sys/geom/vinum/geom_vinum_plex.c b/sys/geom/vinum/geom_vinum_plex.c
--- a/sys/geom/vinum/geom_vinum_plex.c
+++ b/sys/geom/vinum/geom_vinum_plex.c
@@ -173,7 +173,7 @@
 			return (GV_ERR_ISBUSY);
 		*sdno = stripeno % sdcount;
 
-		KASSERT(sdno >= 0, ("gv_plex_offset: sdno < 0"));
+		KASSERT(*sdno >= 0, ("gv_plex_offset: sdno < 0"));
 		stripestart = (stripeno / sdcount) *
 		    p->stripesize;
 		KASSERT(stripestart >= 0, ("gv_plex_offset: stripestart < 0"));
diff --git a/sys/geom/vinum/geom_vinum_raid5.c b/sys/geom/vinum/geom_vinum_raid5.c
--- a/sys/geom/vinum/geom_vinum_raid5.c
+++ b/sys/geom/vinum/geom_vinum_raid5.c
@@ -602,7 +602,7 @@
 	/* The number of the subdisk containing the parity stripe. */
 	psd = sdcount - 1 - ( boff / (p->stripesize * (sdcount - 1))) %
 	    sdcount;
-	KASSERT(psdno >= 0, ("gv_raid5_offset: psdno < 0"));
+	KASSERT(psd >= 0, ("gv_raid5_offset: psdno < 0"));
 
 	/* Offset of the start address from the start of the stripe. */
 	stripeoff = boff % (p->stripesize * (sdcount - 1));
@@ -610,7 +610,7 @@
 
 	/* The number of the subdisk where the stripe resides. */
 	sd = stripeoff / p->stripesize;
-	KASSERT(sdno >= 0, ("gv_raid5_offset: sdno < 0"));
+	KASSERT(sd >= 0, ("gv_raid5_offset: sdno < 0"));
 
 	/* At or past parity subdisk. */
 	if (sd >= psd)