diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index 1c8c4d3fa2b4..87bfd9fc47c1 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -849,7 +849,9 @@ ffs_mountfs(devvp, mp, td)
 	 * Our bufobj must require giant for snapshots when quotas are
 	 * enabled.
 	 */
+	BO_LOCK(&devvp->v_bufobj);
 	devvp->v_bufobj.bo_flag |= BO_NEEDSGIANT;
+	BO_UNLOCK(&devvp->v_bufobj);
 #else
 	MNT_ILOCK(mp);
 	mp->mnt_kern_flag |= MNTK_MPSAFE;