diff --git a/lib/libc/gen/getentropy.c b/lib/libc/gen/getentropy.c
index e87796ace58c..ff5475f9fdb0 100644
--- a/lib/libc/gen/getentropy.c
+++ b/lib/libc/gen/getentropy.c
@@ -1,76 +1,77 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2018 Conrad Meyer <cem@FreeBSD.org>
  * 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.
  */
 
 #include <sys/param.h>
 #include <sys/random.h>
 
 #include <errno.h>
 #include <signal.h>
+#include <unistd.h>
 #include <ssp/ssp.h>
 
 #include "libc_private.h"
 
 static inline void
 _getentropy_fail(void)
 {
 	raise(SIGKILL);
 }
 
 int
 __ssp_real(getentropy)(void *buf, size_t buflen)
 {
 	ssize_t rd;
 
 	if (buflen > 256) {
 		errno = EIO;
 		return (-1);
 	}
 
 	while (buflen > 0) {
 		rd = getrandom(buf, buflen, 0);
 		if (rd == -1) {
 			switch (errno) {
 			case EINTR:
 				continue;
 			case EFAULT:
 				return (-1);
 			default:
 				_getentropy_fail();
 			}
 		}
 
 		/* This cannot happen. */
 		if (rd == 0)
 			_getentropy_fail();
 
 		buf = (char *)buf + rd;
 		buflen -= rd;
 	}
 
 	return (0);
 }