diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -5897,6 +5897,8 @@
 static void
 vop_fsync_debugprepost(struct vnode *vp, const char *name)
 {
+	struct mount *mp;
+
 	if (vp->v_type == VCHR)
 		;
 	/*
@@ -5914,10 +5916,16 @@
 	 * should still be caught when the stacked filesystem
 	 * invokes VOP_FSYNC() on the underlying filesystem.
 	 */
-	else if (MNT_SHARED_WRITES(vp->v_mount))
-		ASSERT_VOP_LOCKED(vp, name);
-	else
-		ASSERT_VOP_ELOCKED(vp, name);
+	else {
+		mp = NULL;
+		VOP_GETWRITEMOUNT(vp, &mp);
+		if (vn_lktype_write(mp, vp) == LK_SHARED)
+			ASSERT_VOP_LOCKED(vp, name);
+		else
+			ASSERT_VOP_ELOCKED(vp, name);
+		if (mp != NULL)
+			vfs_rel(mp);
+	}
 }
 
 void