diff --git a/sys/sys/select.h b/sys/sys/select.h
index 9b734754b944..fefc9961d63a 100644
--- a/sys/sys/select.h
+++ b/sys/sys/select.h
@@ -1,134 +1,134 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1992, 1993
  *	The Regents of the University of California.  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. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
  */
 
 #ifndef _SYS_SELECT_H_
 #define	_SYS_SELECT_H_
 
 #include <sys/cdefs.h>
 #include <sys/_types.h>
 
 #include <sys/_sigset.h>
 #include <sys/_timeval.h>
 #include <sys/timespec.h>
 
 typedef	unsigned long	__fd_mask;
 #if __BSD_VISIBLE
 typedef	__fd_mask	fd_mask;
 #endif
 
 #ifndef _SIGSET_T_DECLARED
 #define	_SIGSET_T_DECLARED
 typedef	__sigset_t	sigset_t;
 #endif
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0
 #include <ssp/ssp.h>
 #else
 #define	__SSP_FORTIFY_LEVEL	0
 #endif
 
 /*
  * Select uses bit masks of file descriptors in longs.  These macros
  * manipulate such bit fields (the filesystem macros use chars).
  * FD_SETSIZE may be defined by the user, but the default here should
  * be enough for most uses.
  */
 #ifndef	FD_SETSIZE
 #define	FD_SETSIZE	1024
 #endif
 
 #define	_NFDBITS	(sizeof(__fd_mask) * 8)	/* bits per mask */
 #if __BSD_VISIBLE
 #define	NFDBITS		_NFDBITS
 #endif
 
 #ifndef _howmany
 #define	_howmany(x, y)	(((x) + ((y) - 1)) / (y))
 #endif
 
 typedef	struct fd_set {
 	__fd_mask	__fds_bits[_howmany(FD_SETSIZE, _NFDBITS)];
 } fd_set;
 #if __BSD_VISIBLE
 #define	fds_bits	__fds_bits
 #endif
 
 #define	__fdset_idx_(p, n)	((n) / _NFDBITS)
 #if __SSP_FORTIFY_LEVEL == 0
 #define	__fdset_idx(p, n)	__fdset_idx_(p, n)
 #else
 __ssp_inline unsigned long
-__fdset_idx(fd_set *p, unsigned long idx)
+__fdset_idx(const fd_set *p, unsigned long idx)
 {
 	__size_t psz = __ssp_bos0(p);
 	unsigned long sidx = __fdset_idx_(p, idx);
 
 	if (idx >= FD_SETSIZE)
 		__chk_fail();
 	if (psz / sizeof(__fd_mask) < (sidx + 1))
 		__chk_fail();
 
 	return (sidx);
 }
 #endif
 
 #define	__fdset_mask(n)	((__fd_mask)1 << ((n) % _NFDBITS))
 #define	FD_CLR(n, p)	((p)->__fds_bits[__fdset_idx(p, n)] &= ~__fdset_mask(n))
 #if __BSD_VISIBLE
 #define	FD_COPY(f, t)	(void)(*(t) = *(f))
 #endif
 #define	FD_ISSET(n, p)	\
     (((p)->__fds_bits[__fdset_idx(p, n)] & __fdset_mask(n)) != 0)
 #define	FD_SET(n, p)	((p)->__fds_bits[__fdset_idx(p, n)] |= __fdset_mask(n))
 #define	FD_ZERO(p) do {					\
 	fd_set *_p;					\
 	__size_t _n;					\
 							\
 	_p = (p);					\
 	_n = _howmany(FD_SETSIZE, _NFDBITS);		\
 	while (_n > 0)					\
 		_p->__fds_bits[--_n] = 0;		\
 } while (0)
 
 #ifndef _KERNEL
 
 __BEGIN_DECLS
 int pselect(int, fd_set *__restrict, fd_set *__restrict, fd_set *__restrict,
 	const struct timespec *__restrict, const sigset_t *__restrict);
 #ifndef _SELECT_DECLARED
 #define	_SELECT_DECLARED
 /* XXX missing restrict type-qualifier */
 int	select(int, fd_set *, fd_set *, fd_set *, struct timeval *);
 #endif
 __END_DECLS
 #endif /* !_KERNEL */
 
 #endif /* _SYS_SELECT_H_ */