diff --git a/check.t b/check.t
index eb4cd16..15d4e4a 100644
--- a/check.t
+++ b/check.t
@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.290 2009/07/06 15:06:23 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.291 2009/07/16 15:06:42 tg Exp $
 # $OpenBSD: bksl-nl.t,v 1.2 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: history.t,v 1.5 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: read.t,v 1.3 2003/03/10 03:48:16 david Exp $
@@ -25,7 +25,7 @@
 # http://www.research.att.com/~gsf/public/ifs.sh
 
 expected-stdout:
-	@(#)MIRBSD KSH R38 2009/07/06
+	@(#)MIRBSD KSH R39 2009/07/16
 description:
 	Check version of shell.
 stdin:
@@ -5875,3 +5875,79 @@ expected-stdout:
 	= 0
 	foo
 ---
+name: nounset-1
+description:
+	Check that "set -u" matches (future) POSIX requirement
+stdin:
+	(set -u
+	try() {
+		local v
+		eval v=\$$1
+		if [[ -n $v ]]; then
+			echo $1=nz
+		else
+			echo $1=zf
+		fi
+	}
+	x=y
+	(echo $x)
+	echo =1
+	(echo $y)
+	echo =2
+	(try x)
+	echo =3
+	(try y)
+	echo =4
+	(try 0)
+	echo =5
+	(try 2)
+	echo =6
+	(try)
+	echo =7
+	(echo at=$@)
+	echo =8
+	(echo asterisk=$*)
+	echo =9
+	(echo $?)
+	echo =10
+	(echo $!)
+	echo =11
+	(echo $-)
+	echo =12
+	#(echo $_)
+	#echo =13
+	(echo $#)
+	echo =14
+	(mypid=$$; try mypid)
+	echo =15
+	) 2>&1 | sed -e 's/^[^]]*]//' -e 's/^[^:]*: *//'
+expected-stdout:
+	y
+	=1
+	y: parameter not set
+	=2
+	x=nz
+	=3
+	y: parameter not set
+	=4
+	0=nz
+	=5
+	2: parameter not set
+	=6
+	1: parameter not set
+	=7
+	at=
+	=8
+	asterisk=
+	=9
+	0
+	=10
+	!: parameter not set
+	=11
+	ush
+	=12
+	0
+	=14
+	mypid=nz
+	=15
+---
diff --git a/eval.c b/eval.c
index 36b84ed..a4b2436 100644
--- a/eval.c
+++ b/eval.c
@@ -22,7 +22,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/eval.c,v 1.60 2009/06/11 12:42:17 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/eval.c,v 1.61 2009/07/16 15:06:43 tg Exp $");
 
 #ifdef MKSH_SMALL
 #define MKSH_NOPWNAM
@@ -913,6 +913,7 @@ varsub(Expand *xp, const char *sp, const char *word,
 	int slen;
 	const char *p;
 	struct tbl *vp;
+	bool zero_ok = false;
 
 	if (sp[0] == '\0')	/* Bad variable name */
 		return (-1);
@@ -921,8 +922,6 @@ varsub(Expand *xp, const char *sp, const char *word,
 
 	/* ${#var}, string length or array size */
 	if (sp[0] == '#' && (c = sp[1]) != '\0') {
-		int zero_ok = 0;
-
 		/* Can't have any modifiers for ${#...} */
 		if (*word != CSUBST)
 			return (-1);
@@ -934,7 +933,7 @@ varsub(Expand *xp, const char *sp, const char *word,
 
 			vp = global(arrayname(sp));
 			if (vp->flag & (ISSET|ARRAY))
-				zero_ok = 1;
+				zero_ok = true;
 			for (; vp; vp = vp->u.array)
 				if (vp->flag & ISSET)
 					n++;
@@ -1005,6 +1004,7 @@ varsub(Expand *xp, const char *sp, const char *word,
 			xp->split = c == '@'; /* $@ */
 			state = XARG;
 		}
+		zero_ok = true;	/* POSIX 2009? */
 	} else {
 		if ((p = cstrchr(sp, '[')) && (p[1] == '*' || p[1] == '@') &&
 		    p[2] == ']') {
@@ -1052,7 +1052,7 @@ varsub(Expand *xp, const char *sp, const char *word,
 	    (((stype&0x80) ? *xp->str=='\0' : xp->str==null) ? /* undef? */
 	    c == '=' || c == '-' || c == '?' : c == '+'))
 		state = XBASE;	/* expand word instead of variable value */
-	if (Flag(FNOUNSET) && xp->str == null &&
+	if (Flag(FNOUNSET) && xp->str == null && !zero_ok &&
 	    (ctype(c, C_SUBOP2) || (state != XBASE && c != '+')))
 		errorf("%s: parameter not set", sp);
 	return (state);
diff --git a/mksh.1 b/mksh.1
index cfd9094..8646c13 100644
--- a/mksh.1
+++ b/mksh.1
@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.173 2009/07/08 10:37:24 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.174 2009/07/16 15:06:44 tg Rel $
 .\" $OpenBSD: ksh.1,v 1.129 2009/05/28 06:09:06 jmc Exp $
 .\"-
 .\" Copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
@@ -48,7 +48,7 @@
 .el .xD \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 \\$7 \\$8
 ..
 .\"-
-.Dd $Mdocdate: July 8 2009 $
+.Dd $Mdocdate: July 16 2009 $
 .Dt MKSH 1
 .Os MirBSD
 .Sh NAME
@@ -3551,7 +3551,11 @@ or
 .Dq utf8 ,
 or if the input begins with a UTF-8 Byte Order Mark.
 .It Fl u \*(Ba Ic nounset
-Referencing of an unset parameter is treated as an error, unless one of the
+Referencing of an unset parameter, other than
+.Dq $@
+or
+.Dq $* ,
+is treated as an error, unless one of the
 .Ql \- ,
 .Ql + ,
 or
@@ -5651,7 +5655,7 @@ all contributors, such as the Debian and OpenBSD projects.
 See the documentation, CVS, and web site for details.
 .Sh BUGS
 This document attempts to describe
-.Nm mksh\ R38
+.Nm mksh\ R39
 and up,
 compiled without any options impacting functionality, such as
 .Dv MKSH_SMALL ,
diff --git a/sh.h b/sh.h
index 9dac010..570ac7b 100644
--- a/sh.h
+++ b/sh.h
@@ -122,9 +122,9 @@
 #define __SCCSID(x)	__IDSTRING(sccsid,x)
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.312 2009/07/06 15:06:25 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.313 2009/07/16 15:06:45 tg Exp $");
 #endif
-#define MKSH_VERSION "R38 2009/07/06"
+#define MKSH_VERSION "R39 2009/07/16"
 
 #ifndef MKSH_INCLUDES_ONLY