Index: usr.sbin/makefs/msdos/Makefile.inc
===================================================================
--- usr.sbin/makefs/msdos/Makefile.inc
+++ usr.sbin/makefs/msdos/Makefile.inc
@@ -6,7 +6,7 @@
 
 .PATH:	${SRCDIR}/msdos ${MSDOS} ${MSDOS_NEWFS}
 
-CFLAGS+= -DMAKEFS -I${MSDOS} -I${MSDOS_NEWFS}
+CFLAGS+= -DMAKEFS -I${MSDOS} -I${MSDOS_NEWFS} -I${SRCDIR}/msdos
 
 SRCS+= mkfs_msdos.c
 SRCS+= msdosfs_conv.c msdosfs_denode.c msdosfs_fat.c msdosfs_lookup.c
Index: usr.sbin/makefs/msdos/msdosfs_denode.c
===================================================================
--- usr.sbin/makefs/msdos/msdosfs_denode.c
+++ usr.sbin/makefs/msdos/msdosfs_denode.c
@@ -67,8 +67,6 @@
 #include <fs/msdosfs/fat.h>
 #include <fs/msdosfs/msdosfsmount.h>
 
-#undef clrbuf
-#include "ffs/buf.h"
 #include "makefs.h"
 #include "msdos.h"
 
Index: usr.sbin/makefs/msdos/msdosfs_fat.c
===================================================================
--- usr.sbin/makefs/msdos/msdosfs_fat.c
+++ usr.sbin/makefs/msdos/msdosfs_fat.c
@@ -65,8 +65,6 @@
 #include <fs/msdosfs/fat.h>
 #include <fs/msdosfs/msdosfsmount.h>
 
-#undef clrbuf
-#include "ffs/buf.h"
 #include "makefs.h"
 #include "msdos.h"
 
Index: usr.sbin/makefs/msdos/msdosfs_lookup.c
===================================================================
--- usr.sbin/makefs/msdos/msdosfs_lookup.c
+++ usr.sbin/makefs/msdos/msdosfs_lookup.c
@@ -63,8 +63,6 @@
 #include <fs/msdosfs/fat.h>
 #include <fs/msdosfs/msdosfsmount.h>
 
-#undef clrbuf
-#include "ffs/buf.h"
 #include "makefs.h"
 #include "msdos.h"
 
Index: usr.sbin/makefs/msdos/msdosfs_vfsops.c
===================================================================
--- usr.sbin/makefs/msdos/msdosfs_vfsops.c
+++ usr.sbin/makefs/msdos/msdosfs_vfsops.c
@@ -70,8 +70,6 @@
 
 #include <mkfs_msdos.h>
 
-#undef clrbuf
-#include "ffs/buf.h"
 #include "makefs.h"
 #include "msdos.h"
 
Index: usr.sbin/makefs/msdos/msdosfs_vnops.c
===================================================================
--- usr.sbin/makefs/msdos/msdosfs_vnops.c
+++ usr.sbin/makefs/msdos/msdosfs_vnops.c
@@ -70,8 +70,6 @@
 #include <fs/msdosfs/fat.h>
 #include <fs/msdosfs/msdosfsmount.h>
 
-#undef clrbuf
-#include "ffs/buf.h"
 #include "makefs.h"
 #include "msdos.h"
 
Index: usr.sbin/makefs/msdos/sys/buf.h
===================================================================
--- /dev/null
+++ usr.sbin/makefs/msdos/sys/buf.h
@@ -0,0 +1,35 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2018-2020 Alex Richardson <arichardson@FreeBSD.org>
+ *
+ * This work was supported by Innovate UK project 105694, "Digital Security by
+ * Design (DSbD) Technology Platform Prototype".
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#pragma once
+#define buf m_buf
+struct vn_clusterw {
+	/* Not interesting for MSDOFS makefs */
+};
+#include "../../ffs/buf.h"