diff --git a/Build.sh b/Build.sh
index 439aa99..b9f1867 100644
--- a/Build.sh
+++ b/Build.sh
@@ -1,5 +1,5 @@
 #!/bin/sh
-srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.520 2012/03/27 23:01:51 tg Exp $'
+srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.521 2012/03/27 23:13:40 tg Exp $'
 #-
 # Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
 #		2011, 2012
@@ -299,6 +299,7 @@ rmf a.exe* a.out* conftest.c *core core.* lft mksh* no *.bc *.ll *.o \
 curdir=`pwd` srcdir=`dirname "$0"` check_categories=
 test -n "$srcdir" || srcdir=.
 dstversion=`sed -n '/define MKSH_VERSION/s/^.*"\(.*\)".*$/\1/p' $srcdir/sh.h`
+add_cppflags -DMKSH_BUILDSH
 
 e=echo
 r=0
@@ -582,8 +583,8 @@ SCO_SV)
 		: ${HAVE_SYS_SIGLIST=0} ${HAVE__SYS_SIGLIST=0}
 		;;
 	*)
-		oswarn='; this is an unknown version'
-		oswarn="$oswarn${nl}of ${TARGET_OS} ${TARGET_OSREV}, please tell me"
+		oswarn='; this is an unknown version of'
+		oswarn="$oswarn$nl$TARGET_OS ${TARGET_OSREV}, please tell me what to do"
 		;;
 	esac
 	;;
@@ -1339,7 +1340,7 @@ else
 		#define EXTERN
 		#define MKSH_INCLUDES_ONLY
 		#include "sh.h"
-		__RCSID("$MirOS: src/bin/mksh/Build.sh,v 1.520 2012/03/27 23:01:51 tg Exp $");
+		__RCSID("$MirOS: src/bin/mksh/Build.sh,v 1.521 2012/03/27 23:13:40 tg Exp $");
 		int main(void) { printf("Hello, World!\n"); return (0); }
 EOF
 	case $cm in
@@ -1773,7 +1774,7 @@ addsrcs '!' HAVE_STRLCPY strlcpy.c
 addsrcs USE_PRINTF_BUILTIN printf.c
 test 1 = "$USE_PRINTF_BUILTIN" && add_cppflags -DMKSH_PRINTF_BUILTIN
 test 1 = "$HAVE_CAN_VERB" && CFLAGS="$CFLAGS -verbose"
-add_cppflags -DMKSH_BUILDSH
+add_cppflags -DMKSH_BUILD_R=409
 
 $e $bi$me: Finished configuration testing, now producing output.$ao
 
diff --git a/Makefile b/Makefile
index 6973a8c..8483ae5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/Makefile,v 1.95 2012/03/27 22:36:49 tg Exp $
+# $MirOS: src/bin/mksh/Makefile,v 1.96 2012/03/27 23:13:41 tg Exp $
 #-
 # Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
 #		2011, 2012
@@ -47,9 +47,8 @@ CPPFLAGS+=	-DMKSH_ASSUME_UTF8 -DMKSH_DISABLE_DEPRECATED \
 		-DHAVE_SELECT=1 -DHAVE_SETRESUGID=1 -DHAVE_SETGROUPS=1 \
 		-DHAVE_STRCASESTR=1 -DHAVE_STRLCPY=1 -DHAVE_FLOCK_DECL=1 \
 		-DHAVE_REVOKE_DECL=1 -DHAVE_SYS_SIGLIST_DECL=1 \
-		-DHAVE_PERSISTENT_HISTORY=1
-# probably differs between i386 and sparc
-CPPFLAGS+=	-DHAVE_SILENT_IDIVWRAPV=0
+		-DHAVE_PERSISTENT_HISTORY=1 -DHAVE_SILENT_IDIVWRAPV=0 \
+		-DMKSH_BUILD_R=409
 CPPFLAGS+=	-D${${PROG:L}_tf:C/(Mir${MAN:E}{0,1}){2}/4/:S/x/mksh_BUILD/:U}
 COPTS+=		-std=c99 -Wall
 .endif
diff --git a/sh.h b/sh.h
index 2f79986..ed5ea3e 100644
--- a/sh.h
+++ b/sh.h
@@ -152,7 +152,7 @@
 #endif
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.534 2012/03/27 22:58:39 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.535 2012/03/27 23:13:42 tg Exp $");
 #endif
 #define MKSH_VERSION "R40 2012/03/27"
 
@@ -442,9 +442,9 @@ char *ucstrstr(char *, const char *);
 #define mkssert(e)	((void)0)
 #endif
 
-#if !defined(MKSH_BUILDMAKEFILE4BSD) && !defined(MKSH_BUILDSH)
-I'm sorry, Dave. I'm afraid I can't do that.
+#if (!defined(MKSH_BUILDMAKEFILE4BSD) && !defined(MKSH_BUILDSH)) || (MKSH_BUILD_R != 409)
 #error Must run Build.sh to compile this.
+I'm sorry, Dave. I'm afraid I can't do that.
 #endif
 
 /* use this ipv strchr(s, 0) but no side effects in s! */