diff --git a/check.t b/check.t
index fa20ed0..792f74c 100644
--- a/check.t
+++ b/check.t
@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.351 2010/01/01 17:44:06 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.352 2010/01/01 18:01:59 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 $
@@ -4460,6 +4460,28 @@ stdin:
 	echo 1- $(runtest utf8-mode) =
 	echo 2- $(runtest !utf8-mode) =
 	echo 3- $(runtest ?utf8-mode) =
+	echo = short flags =
+	echo 0y $(if_test -U) =
+	echo 0y $(if_test +U) =
+	echo 0n $(if_test -_) =
+	echo 0n $(if_test -U-) =
+	echo 1= $(runtest -_) =
+	echo 2= $(runtest !-_) =
+	echo 3= $(runtest ?-_) =
+	set +U
+	echo 1+ $(runtest -U) =
+	echo 2+ $(runtest !-U) =
+	echo 3+ $(runtest ?-U) =
+	echo 1+ $(runtest +U) =
+	echo 2+ $(runtest !+U) =
+	echo 3+ $(runtest ?+U) =
+	set -U
+	echo 1- $(runtest -U) =
+	echo 2- $(runtest !-U) =
+	echo 3- $(runtest ?-U) =
+	echo 1- $(runtest +U) =
+	echo 2- $(runtest !+U) =
+	echo 3- $(runtest ?+U) =
 expected-stdout:
 	0y 0 0 0 0 =
 	0n 1 1 1 1 =
@@ -4472,6 +4494,26 @@ expected-stdout:
 	1- 0 0 0 =
 	2- 1 1 1 =
 	3- 0 0 0 =
+	= short flags =
+	0y 0 0 0 0 =
+	0y 0 0 0 0 =
+	0n 1 1 1 1 =
+	0n 1 1 1 1 =
+	1= 1 1 1 =
+	2= 1 1 1 =
+	3= 1 1 1 =
+	1+ 1 1 1 =
+	2+ 0 0 0 =
+	3+ 0 0 0 =
+	1+ 1 1 1 =
+	2+ 0 0 0 =
+	3+ 0 0 0 =
+	1- 0 0 0 =
+	2- 1 1 1 =
+	3- 0 0 0 =
+	1- 0 0 0 =
+	2- 1 1 1 =
+	3- 0 0 0 =
 ---
 name: mkshrc-1
 description:
diff --git a/misc.c b/misc.c
index 914ee7c..1c80fa7 100644
--- a/misc.c
+++ b/misc.c
@@ -29,7 +29,7 @@
 #include <grp.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/misc.c,v 1.134 2009/12/05 17:43:48 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/misc.c,v 1.135 2010/01/01 18:02:00 tg Exp $");
 
 unsigned char chtypes[UCHAR_MAX + 1];	/* type bits for unsigned char */
 
@@ -108,7 +108,11 @@ option(const char *n)
 {
 	size_t i;
 
-	for (i = 0; i < NELEM(options); i++)
+	if ((n[0] == '-' || n[0] == '+') && n[1] && !n[2]) {
+		for (i = 0; i < NELEM(options); i++)
+			if (options[i].c == n[1])
+				return (i);
+	} else for (i = 0; i < NELEM(options); i++)
 		if (options[i].name && strcmp(options[i].name, n) == 0)
 			return (i);
 
diff --git a/mksh.1 b/mksh.1
index b0ede6f..0d86544 100644
--- a/mksh.1
+++ b/mksh.1
@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.203 2010/01/01 17:44:08 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.204 2010/01/01 18:02:01 tg Exp $
 .\" $OpenBSD: ksh.1,v 1.129 2009/05/28 06:09:06 jmc Exp $
 .\"-
 .\" Copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
@@ -3911,7 +3911,8 @@ Enable
 mode.
 Automatically enabled if the basename of the shell invocation begins with
 .Dq sh
-and this autodetection feature was requested at compilation time.
+and this autodetection feature was requested at compilation time
+.Pq not in MirBSD .
 As a side effect, setting this flag turns off
 .Ic braceexpand
 mode, which can be turned back on manually.
@@ -4061,6 +4062,18 @@ exists).
 The same can be achieved with [ \-o ?foo ] like in
 .At
 .Nm ksh93 .
+.Ar option
+can also be the short flag led by either
+.Ql \-
+or
+.Ql +
+.Pq no logical negation ,
+for example
+.Ql \-x
+or
+.Ql +x
+instead of
+.Ql xtrace .
 .It Fl p Ar file
 .Ar file
 is a named pipe.