diff --git a/ChangeLog b/ChangeLog
index b5e2a60..a3188fa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2017-09-12  Ben Elliston  <bje@gnu.org>
+
+	* config.sub (maybe_os): Remove -windowsnt*.
+	* config.guess (Alpha\ *:Windows_NT*:*): Remove obsolete case.
+	(21064:Windows_NT:50:3): Likewise.
+	(i*:windows32*:*): Likewise.
+	([345]86:Windows_95:*, [345]86:Windows_98:*): Likewise.
+	([345]86:Windows_NT:*): Likewise.
+	(8664:Windows_NT:*): Likewise.
+	(i*:Windows_NT*:* | Pentium*:Windows_NT*:*): Likewise.
+	(p*:CYGWIN*:*): Likewise.
+	* testsuite/config-guess.data: Remove relevant test cases.
+
 2017-09-10  Ben Elliston  <bje@gnu.org>
 
 	* config.sub: Improve comments.
diff --git a/config.guess b/config.guess
index a744844..7834a66 100755
--- a/config.guess
+++ b/config.guess
@@ -2,7 +2,7 @@
 # Attempt to guess a canonical system name.
 #   Copyright 1992-2017 Free Software Foundation, Inc.
 
-timestamp='2017-08-08'
+timestamp='2017-09-12'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -318,15 +318,6 @@ case "${UNAME_MACHINE}:${UNAME_SYSTEM}:${UNAME_RELEASE}:${UNAME_VERSION}" in
 	exitcode=$?
 	trap '' 0
 	exit $exitcode ;;
-    Alpha\ *:Windows_NT*:*)
-	# How do we know it's Interix rather than the generic POSIX subsystem?
-	# Should we change UNAME_MACHINE based on the output of uname instead
-	# of the specific Alpha model?
-	echo alpha-pc-interix
-	exit ;;
-    21064:Windows_NT:50:3)
-	echo alpha-dec-winnt3.5
-	exit ;;
     Amiga*:UNIX_System_V:4.0:*)
 	echo m68k-unknown-sysv4
 	exit ;;
@@ -858,10 +849,6 @@ EOF
     *:MSYS*:*)
 	echo ${UNAME_MACHINE}-pc-msys
 	exit ;;
-    i*:windows32*:*)
-	# uname -m includes "-pc" on this system.
-	echo ${UNAME_MACHINE}-mingw32
-	exit ;;
     i*:PW*:*)
 	echo ${UNAME_MACHINE}-pc-pw32
 	exit ;;
@@ -877,27 +864,12 @@ EOF
 		echo ia64-unknown-interix${UNAME_RELEASE}
 		exit ;;
 	esac ;;
-    [345]86:Windows_95:* | [345]86:Windows_98:* | [345]86:Windows_NT:*)
-	echo i${UNAME_MACHINE}-pc-mks
-	exit ;;
-    8664:Windows_NT:*)
-	echo x86_64-pc-mks
-	exit ;;
-    i*:Windows_NT*:* | Pentium*:Windows_NT*:*)
-	# How do we know it's Interix rather than the generic POSIX subsystem?
-	# It also conflicts with pre-2.0 versions of AT&T UWIN. Should we
-	# UNAME_MACHINE based on the output of uname instead of i386?
-	echo i586-pc-interix
-	exit ;;
     i*:UWIN*:*)
 	echo ${UNAME_MACHINE}-pc-uwin
 	exit ;;
     amd64:CYGWIN*:*:* | x86_64:CYGWIN*:*:*)
 	echo x86_64-unknown-cygwin
 	exit ;;
-    p*:CYGWIN*:*)
-	echo powerpcle-unknown-cygwin
-	exit ;;
     prep*:SunOS:5.*:*)
 	echo powerpcle-unknown-solaris2`echo ${UNAME_RELEASE}|sed -e 's/[^.]*//'`
 	exit ;;
diff --git a/config.sub b/config.sub
index 56257ad..8d2c203 100755
--- a/config.sub
+++ b/config.sub
@@ -2,7 +2,7 @@
 # Configuration validation subroutine script.
 #   Copyright 1992-2017 Free Software Foundation, Inc.
 
-timestamp='2017-09-10'
+timestamp='2017-09-12'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -229,9 +229,6 @@ case $os in
 	-ptx*)
 		basic_machine=`echo $1 | sed -e 's/86-.*/86-sequent/'`
 		;;
-	-windowsnt*)
-		os=`echo $os | sed -e 's/windowsnt/winnt/'`
-		;;
 	-psos*)
 		os=-psos
 		;;
diff --git a/testsuite/config-guess.data b/testsuite/config-guess.data
index 1ce2a74..9b78279 100644
--- a/testsuite/config-guess.data
+++ b/testsuite/config-guess.data
@@ -1,6 +1,5 @@
 2064		 ignored		 z/VM			 ignored	 ignored	 s390-ibm-zvmoe
 3		 2.3.3			 XENIX			 SysV		 ignored	 i386-pc-xenix
-8664		 1.0			 Windows_NT		 ignored	 ignored	 x86_64-pc-mks
 aarch64_be	 ignored		 Linux			 ignored	 ignored	 aarch64_be-unknown-linux-gnu
 aarch64		 ignored		 Linux			 ignored	 ignored	 aarch64-unknown-linux-gnu
 amd64		 1.5.12(0.116/4/2)	 CYGWIN_NT-5.2		 ignored	 ignored	 x86_64-unknown-cygwin
@@ -47,7 +46,6 @@ i586		 ignored		 rdos			 ignored	 ignored	 i586-pc-rdos
 i686		 1.0.17(0.48/3/2)	 MSYS_NT-6.0		 ignored	 ignored	 i686-pc-msys
 i686		 5.11-686		 GNU/kOpenSolaris	 ignored	 ignored	 i686-unknown-kopensolaris5.11-gnu
 i686		 5.4-1-686		 GNU/kFreeBSD		 ignored	 ignored	 i686-unknown-kfreebsd5.4-gnu
-i786-pc		 ignored		 windows32		 ignored	 ignored	 i786-pc-mingw32
 i86pc		 5.0			 AuroraUX		 ignored	 ignored	 i386-pc-auroraux5.0
 i86xen		 5.0			 AuroraUX		 ignored	 ignored	 i386-pc-auroraux5.0
 IA64		 6.0			 Interix		 ignored	 ignored	 ia64-unknown-interix6.0