diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 60d3a71667a..475467da3c3 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -2659,6 +2659,9 @@ sync_vnode(struct synclist *slp, struct bufobj **bo, struct thread *td)
 		mtx_lock(&sync_mtx);
 		return (*bo == LIST_FIRST(slp));
 	}
+	MPASSERT(mp == NULL || (curthread->td_pflags & TDP_IGNSUSP) != 0 ||
+	    (mp->mnt_kern_flag & MNTK_SUSPENDED) == 0, mp,
+	    ("suspended mp syncing vp %p", vp));
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	(void) VOP_FSYNC(vp, MNT_LAZY, td);
 	VOP_UNLOCK(vp);