diff --git a/ChangeLog b/ChangeLog
index e24f73274..89bfa66a1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,9 @@
     the pty master on Solaris, since it never succeeds and can hang if large
     amounts of data is sent to the slave (eg a copy-paste).  Based on a patch
     originally from Doke Scott, ok djm@
+ - (dtucker) [clientloop.c configure.ac defines.h] Make the client's IO buffer
+   size a compile-time option and set it to 64k on Cygwin, since Corinna
+   reports that it makes a significant difference to performance.  ok djm@
 
 20090820
  - (dtucker) [includes.h] Bug #1634: do not include system glob.h if we're not
diff --git a/clientloop.c b/clientloop.c
index b8352f6bf..9a7dc0ab0 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -636,7 +636,7 @@ static void
 client_process_net_input(fd_set *readset)
 {
 	int len, cont = 0;
-	char buf[8192];
+	char buf[SSH_IOBUFSZ];
 
 	/*
 	 * Read input from the server, and add any such data to the buffer of
@@ -1129,7 +1129,7 @@ static void
 client_process_input(fd_set *readset)
 {
 	int len;
-	char buf[8192];
+	char buf[SSH_IOBUFSZ];
 
 	/* Read input from stdin. */
 	if (FD_ISSET(fileno(stdin), readset)) {
diff --git a/configure.ac b/configure.ac
index 5f5a08a0a..ef0b0fc97 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,4 +1,4 @@
-# $Id: configure.ac,v 1.423 2009/08/28 01:02:37 dtucker Exp $
+# $Id: configure.ac,v 1.424 2009/08/28 01:21:07 dtucker Exp $
 #
 # Copyright (c) 1999-2004 Damien Miller
 #
@@ -15,7 +15,7 @@
 # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 AC_INIT(OpenSSH, Portable, openssh-unix-dev@mindrot.org)
-AC_REVISION($Revision: 1.423 $)
+AC_REVISION($Revision: 1.424 $)
 AC_CONFIG_SRCDIR([ssh.c])
 
 AC_CONFIG_HEADER(config.h)
@@ -446,6 +446,7 @@ int main(void) { exit(0); }
 	AC_DEFINE(DISABLE_FD_PASSING, 1,
 		[Define if your platform needs to skip post auth
 		file descriptor passing])
+	AC_DEFINE(SSH_IOBUFSZ, 65536, [Windows is sensitive to read buffer size])
 	;;
 *-*-dgux*)
 	AC_DEFINE(IP_TOS_IS_BROKEN, 1,
diff --git a/defines.h b/defines.h
index 2ccded266..2ddfd96d0 100644
--- a/defines.h
+++ b/defines.h
@@ -25,7 +25,7 @@
 #ifndef _DEFINES_H
 #define _DEFINES_H
 
-/* $Id: defines.h,v 1.155 2009/06/16 06:11:02 dtucker Exp $ */
+/* $Id: defines.h,v 1.156 2009/08/28 01:21:07 dtucker Exp $ */
 
 
 /* Constants */
@@ -749,4 +749,8 @@ struct winsize {
 #define INET6_ADDRSTRLEN 46
 #endif
 
+#ifndef SSH_IOBUFSZ
+# define SSH_IOBUFSZ 8192
+#endif
+
 #endif /* _DEFINES_H */