Index: head/sbin/geom/class/virstor/geom_virstor.c
===================================================================
--- head/sbin/geom/class/virstor/geom_virstor.c
+++ head/sbin/geom/class/virstor/geom_virstor.c
@@ -183,6 +183,7 @@
 		goto out;
 	}
 	bcopy(md, sector, size);
+	bzero(sector + size, sectorsize - size);
 	if (pwrite(fd, sector, sectorsize, mediasize - sectorsize) !=
 	    (ssize_t)sectorsize) {
 		error = errno;
Index: head/sbin/geom/misc/subr.c
===================================================================
--- head/sbin/geom/misc/subr.c
+++ head/sbin/geom/misc/subr.c
@@ -302,6 +302,7 @@
 		goto out;
 	}
 	bcopy(md, sector, size);
+	bzero(sector + size, sectorsize - size);
 	if (pwrite(fd, sector, sectorsize, mediasize - sectorsize) !=
 	    sectorsize) {
 		error = errno;