diff --git a/tools/build/libc-bootstrap/namespace.h b/tools/build/libc-bootstrap/namespace.h
index 73e27f8cb02b..2c242f88072d 100644
--- a/tools/build/libc-bootstrap/namespace.h
+++ b/tools/build/libc-bootstrap/namespace.h
@@ -1,52 +1,54 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright 2018-2020 Alex Richardson <arichardson@FreeBSD.org>
  *
  * This software was developed by SRI International and the University of
  * Cambridge Computer Laboratory (Department of Computer Science and
  * Technology) under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the
  * DARPA SSITH research programme.
  *
  * This software was developed by SRI International and the University of
  * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
  * ("CTSRD"), as part of the DARPA CRASH research programme.
  *
  * 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.
  *
  * $FreeBSD$
  */
 #pragma once
 
 #define _open(...)	open(__VA_ARGS__)
 #define _close(a)	close(a)
 #define _fstat(a, b)	fstat(a, b)
 #define _read(a, b, c)	read(a, b, c)
 #define _write(a, b, c)	write(a, b, c)
 #define _writev(a, b, c)	writev(a, b, c)
 #define _fsync(a)	fsync(a)
 #define	_getprogname()	getprogname()
-#define	_err(...)	err(__VA_ARGS__)
+/* These two need to be renamed to build libc/gen/err.c */
+#define	err	_err
+#define	warn	_warn
 
 #define _pthread_mutex_unlock	pthread_mutex_unlock
 #define _pthread_mutex_lock	pthread_mutex_lock
 
diff --git a/tools/build/libc-bootstrap/un-namespace.h b/tools/build/libc-bootstrap/un-namespace.h
index 398707791792..f08ab41ea543 100644
--- a/tools/build/libc-bootstrap/un-namespace.h
+++ b/tools/build/libc-bootstrap/un-namespace.h
@@ -1,40 +1,43 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright 2018-2020 Alex Richardson <arichardson@FreeBSD.org>
  *
  * This software was developed by SRI International and the University of
  * Cambridge Computer Laboratory (Department of Computer Science and
  * Technology) under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the
  * DARPA SSITH research programme.
  *
  * This software was developed by SRI International and the University of
  * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
  * ("CTSRD"), as part of the DARPA CRASH research programme.
  *
  * 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.
  *
  * $FreeBSD$
  */
 #pragma once
-/* This can be empty when building the FreeBSD compatible bootstrap files */
+
+/* Undo the changes made by namespace.h */
+#undef	err
+#undef	warn