diff --git a/compat/getdtablesize.c b/compat/getdtablesize.c
new file mode 100644
index 00000000..fa82577f
--- /dev/null
+++ b/compat/getdtablesize.c
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2020 Nicholas Marriott <nicholas.marriott@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+
+#include <unistd.h>
+
+#include "compat.h"
+
+#ifdef HAVE_SYSCONF
+int
+getdtablesize(void)
+{
+	return (sysconf(_SC_OPEN_MAX));
+}
+#endif
diff --git a/compat/imsg-buffer.c b/compat/imsg-buffer.c
index 814591f4..67d4c705 100644
--- a/compat/imsg-buffer.c
+++ b/compat/imsg-buffer.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: imsg-buffer.c,v 1.11 2017/12/14 09:27:44 kettenis Exp $	*/
+/*	$OpenBSD: imsg-buffer.c,v 1.12 2019/01/20 02:50:03 bcook Exp $	*/
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -70,7 +70,7 @@ ibuf_dynamic(size_t len, size_t max)
 static int
 ibuf_realloc(struct ibuf *buf, size_t len)
 {
-	u_char	*b;
+	unsigned char	*b;
 
 	/* on static buffers max is eq size and so the following fails */
 	if (buf->wpos + len > buf->max) {
diff --git a/compat/imsg.h b/compat/imsg.h
index 8bf94147..5b092cfc 100644
--- a/compat/imsg.h
+++ b/compat/imsg.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: imsg.h,v 1.4 2017/03/24 09:34:12 nicm Exp $	*/
+/*	$OpenBSD: imsg.h,v 1.5 2019/01/20 02:50:03 bcook Exp $	*/
 
 /*
  * Copyright (c) 2006, 2007 Pierre-Yves Ritschard <pyr@openbsd.org>
@@ -21,13 +21,15 @@
 #ifndef _IMSG_H_
 #define _IMSG_H_
 
+#include <stdint.h>
+
 #define IBUF_READ_SIZE		65535
 #define IMSG_HEADER_SIZE	sizeof(struct imsg_hdr)
 #define MAX_IMSGSIZE		16384
 
 struct ibuf {
 	TAILQ_ENTRY(ibuf)	 entry;
-	u_char			*buf;
+	unsigned char		*buf;
 	size_t			 size;
 	size_t			 max;
 	size_t			 wpos;
@@ -42,8 +44,8 @@ struct msgbuf {
 };
 
 struct ibuf_read {
-	u_char			 buf[IBUF_READ_SIZE];
-	u_char			*rptr;
+	unsigned char		 buf[IBUF_READ_SIZE];
+	unsigned char		*rptr;
 	size_t			 wpos;
 };
 
diff --git a/configure.ac b/configure.ac
index 8f26cabd..93246fc8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -113,6 +113,7 @@ AC_REPLACE_FUNCS([ \
 	fgetln \
 	freezero \
 	getdtablecount \
+	getdtablesize \
 	getline \
 	getprogname \
 	memmem \