diff --git a/include/Makefile b/include/Makefile
index ef1af38ca29b..b79204ae77c8 100644
--- a/include/Makefile
+++ b/include/Makefile
@@ -26,9 +26,8 @@ INCS=	a.out.h ar.h assert.h bitstring.h complex.h cpio.h ctype.h db.h \
 
 MHDRS=	float.h floatingpoint.h stdarg.h varargs.h
 
-# posix4/aio.h conflicts with dysons and isn't installed,
 # posix4/mqueue.h is useless without an implementation and isn't installed:
-PHDRS=	sched.h semaphore.h _semaphore.h # aio.h mqueue.h
+PHDRS=	sched.h semaphore.h _semaphore.h # mqueue.h
 
 LHDRS=	aio.h errno.h fcntl.h linker_set.h poll.h stdint.h syslog.h \
 	termios.h ucontext.h
diff --git a/sys/posix4/aio.h b/sys/posix4/aio.h
deleted file mode 100644
index 093eb0bd2dcb..000000000000
--- a/sys/posix4/aio.h
+++ /dev/null
@@ -1,110 +0,0 @@
-/* XXX Conflicts with John's - not installed.
- */
-/*-
- * Copyright (c) 1996, 1997
- *	HD Associates, Inc.  All rights reserved.
- *
- * 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.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by HD Associates, Inc
- * 4. Neither the name of the author nor the names of any co-contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES 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 HD ASSOCIATES 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.
- *
- * $FreeBSD$
- */
-
-/* aio.h: P1003.1B-1993 Asynchronous I/O */
-
-#ifndef _P1003_1B_AIO_H_
-#define _P1003_1B_AIO_H_
-
-#include <sys/_posix.h>
-#include <sys/types.h>
-
-/* For struct sigevent:
- */
-#ifdef _KERNEL
-#include <sys/signal.h>
-#else
-#include <signal.h>
-
-#ifdef _P1003_1B_INCLUDE_MAYBES
-#include <time.h>
-#include <fcntl.h>
-#else
-struct timespec;
-#endif
-#endif
-
-/* Return values: */
-
-#define AIO_CANCELED		0x01	/* All operations cancelled */
-#define AIO_NOTCANCELLED	0x02	/* Some not cancelled */
-#define AIO_ALLDONE		0x04	/* None were cancelled */
-
-/* lio_listio synchronization options */
-
-#define LIO_WAIT		0x08	/* Suspend until complete */
-#define LIO_NOWAIT		0x10	/* Continue operation */
-
-/* lio_listio element operations */
-
-#define LIO_READ		0x20
-#define LIO_WRITE		0x40
-#define LIO_NOP			0x80
-
-typedef struct aiocb * const aio_listio_ctl;
-typedef const struct aiocb * const caio_listio_ctl;
-
-struct aiocb {
-	int		aio_fildes;	/* File descriptor */
-	off_t		aio_offset;	/* File offset */
-	volatile void *	aio_buf;	/* Location of buffer */
-	size_t		aio_nbytes;	/* Length of transfer */
-	int		aio_reqprio;	/* Request priority offset */
-	struct sigevent	aio_sigevent;	/* Signal number and value */
-	int		aio_lio_opcode;	/* Operation to be performed */
-};
-
-#ifndef _KERNEL
-#include <sys/cdefs.h>
-
-__BEGIN_DECLS
-int aio_read(struct aiocb *);
-int aio_write(struct aiocb *);
-
-int lio_listio(int, aio_listio_ctl[], int, struct sigevent *);
-
-int aio_error(const struct aiocb *);
-ssize_t aio_return(struct aiocb *);
-int aio_cancel(int, struct aiocb *);
-
-int aio_suspend(caio_listio_ctl[], int, const struct timespec *);
-
-int aio_fsync(int, struct aiocb *);
-__END_DECLS
-
-#endif /* _KERNEL */
-
-#endif /* _P1003_1B_AIO_H_ */