diff --git a/sys/dev/aac/aac_compat.h b/sys/dev/aac/aac_compat.h
deleted file mode 100644
index ef61c0a36503..000000000000
--- a/sys/dev/aac/aac_compat.h
+++ /dev/null
@@ -1,64 +0,0 @@
-/*-
- * Copyright (c) 2000 Michael Smith
- * Copyright (c) 2000 BSDi
- * 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.
- *
- * 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.
- *
- * $FreeBSD$
- */
-/*
- * Backwards compatibility support.
- */
-
-/*
- * Handle the new/old bio/buf changeover
- */
-
-#if __FreeBSD_version < 500003		/* old buf style */
-#include <sys/buf.h>
-#define FREEBSD_4
-#define bio					buf
-#define bioq_init(x)				bufq_init(x)
-#define bioq_insert_tail(x, y)			bufq_insert_tail(x, y)
-#define bioq_remove(x, y)			bufq_remove(x, y)
-#define bioq_first(x)				bufq_first(x)
-#define bio_queue_head				buf_queue_head
-#define bio_bcount				b_bcount
-#define bio_blkno				b_blkno
-#define bio_caller1				b_caller1
-#define bio_data				b_data
-#define bio_dev					b_dev
-#define bio_driver1				b_driver1
-#define bio_driver2				b_driver2
-#define bio_error				b_error
-#define bio_flags				b_flags
-#define bio_pblkno				b_pblkno
-#define bio_resid				b_resid
-#define BIO_ERROR				B_ERROR
-#define devstat_end_transaction_bio(x, y)      devstat_end_transaction_buf(x, y)
-#define BIO_IS_READ(x)				((x)->b_flags & B_READ)
-
-#else					/* new bio style */
-#include <sys/bio.h>
-#define BIO_IS_READ(x)				((x)->bio_cmd == BIO_READ)
-#endif
diff --git a/sys/dev/aac/aac_debug.c b/sys/dev/aac/aac_debug.c
index 595874538cfb..699f62b6f508 100644
--- a/sys/dev/aac/aac_debug.c
+++ b/sys/dev/aac/aac_debug.c
@@ -45,7 +45,6 @@ __FBSDID("$FreeBSD$");
 #include <machine/resource.h>
 #include <machine/bus.h>
 
-#include <dev/aac/aac_compat.h>
 #include <dev/aac/aacreg.h>
 #include <sys/aac_ioctl.h>
 #include <dev/aac/aacvar.h>