diff --git a/tools/build/Makefile b/tools/build/Makefile
--- a/tools/build/Makefile
+++ b/tools/build/Makefile
@@ -304,6 +304,8 @@
 SYSINCS+=	${SRCTOP}/sys/sys/kbio.h
 # for kldxref:
 SYSINCS+=	${SRCTOP}/sys/sys/module.h
+# for libmd:
+SYSINCS+=	${SRCTOP}/sys/sys/md4.h
 
 # We want to run the build with only ${WORLDTMP} in $PATH to ensure we don't
 # accidentally run tools that are incompatible but happen to be in $PATH.
diff --git a/tools/build/cross-build/include/common/sys/md4.h b/tools/build/cross-build/include/common/sys/md4.h
deleted file mode 100644
--- a/tools/build/cross-build/include/common/sys/md4.h
+++ /dev/null
@@ -1,91 +0,0 @@
-/* MD4.H - header file for MD4C.C
- */
-
-/*-
-   SPDX-License-Identifier: RSA-MD
-
-   Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
-   rights reserved.
-
-   License to copy and use this software is granted provided that it
-   is identified as the "RSA Data Security, Inc. MD4 Message-Digest
-   Algorithm" in all material mentioning or referencing this software
-   or this function.
-   License is also granted to make and use derivative works provided
-   that such works are identified as "derived from the RSA Data
-   Security, Inc. MD4 Message-Digest Algorithm" in all material
-   mentioning or referencing the derived work.
-
-   RSA Data Security, Inc. makes no representations concerning either
-   the merchantability of this software or the suitability of this
-   software for any particular purpose. It is provided "as is"
-   without express or implied warranty of any kind.
-
-   These notices must be retained in any copies of any part of this
-   documentation and/or software.
- */
-
-#ifndef _SYS_MD4_H_
-#define _SYS_MD4_H_
-/* MD4 context. */
-typedef struct MD4Context {
-  u_int32_t state[4];	/* state (ABCD) */
-  u_int32_t count[2];	/* number of bits, modulo 2^64 (lsb first) */
-  unsigned char buffer[64];	/* input buffer */
-} MD4_CTX;
-
-#include <sys/cdefs.h>
-
-#ifndef _KERNEL
-
-/* Ensure libmd symbols do not clash with libcrypto */
-
-#ifndef MD4Init
-#define MD4Init		_libmd_MD4Init
-#endif
-#ifndef MD4Update
-#define MD4Update	_libmd_MD4Update
-#endif
-#ifndef MD4Pad
-#define MD4Pad		_libmd_MD4Pad
-#endif
-#ifndef MD4Final
-#define MD4Final	_libmd_MD4Final
-#endif
-#ifndef MD4End
-#define MD4End		_libmd_MD4End
-#endif
-#ifndef MD4Fd
-#define MD4Fd		_libmd_MD4Fd
-#endif
-#ifndef MD4FdChunk
-#define MD4FdChunk	_libmd_MD4FdChunk
-#endif
-#ifndef MD4File
-#define MD4File		_libmd_MD4File
-#endif
-#ifndef MD4FileChunk
-#define MD4FileChunk	_libmd_MD4FileChunk
-#endif
-#ifndef MD4Data
-#define MD4Data		_libmd_MD4Data
-#endif
-
-#endif
-
-__BEGIN_DECLS
-void   MD4Init(MD4_CTX *);
-void   MD4Update(MD4_CTX *, const unsigned char *, unsigned int);
-void   MD4Pad(MD4_CTX *);
-void   MD4Final(unsigned char [__min_size(16)], MD4_CTX *);
-#ifndef _KERNEL
-char * MD4End(MD4_CTX *, char *);
-char * MD4Fd(int, char *);
-char * MD4FdChunk(int, char *, off_t, off_t);
-char * MD4File(const char *, char *);
-char * MD4FileChunk(const char *, char *, off_t, off_t);
-char * MD4Data(const void *, unsigned int, char *);
-#endif
-__END_DECLS
-
-#endif /* _SYS_MD4_H_ */