diff --git a/config.sub b/config.sub
index 98af000..ea05c2e 100755
--- a/config.sub
+++ b/config.sub
@@ -4,7 +4,7 @@
 
 # shellcheck disable=SC2006,SC2268 # see below for rationale
 
-timestamp='2023-08-07'
+timestamp='2023-08-16'
 
 # 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
@@ -1200,6 +1200,7 @@ case $cpu-$vendor in
 			| d10v | d30v | dlx | dsp16xx \
 			| e2k | elxsi | epiphany \
 			| f30[01] | f700 | fido | fr30 | frv | ft32 | fx80 \
+			| javascript \
 			| h8300 | h8500 \
 			| hppa | hppa1.[01] | hppa2.0 | hppa2.0[nw] | hppa64 \
 			| hexagon \
@@ -1728,6 +1729,9 @@ case $os in
 	# VxWorks passes extra cpu info in the 4th filed.
 	simlinux | simwindows | spe)
 		;;
+	# See `case $cpu-$os` validation below
+	ghcjs)
+		;;
 	# Now accept the basic system types.
 	# The portable systems comes first.
 	# Each alternative MUST end in a * to match a version number.
@@ -1797,6 +1801,20 @@ case $obj in
 		;;
 esac
 
+# Here we handle the constraint that a (synthetic) cpu and os are
+# valid only in combination with each other and nowhere else.
+case $cpu-$os in
+	# The "javascript-unknown-ghcjs" triple is used by GHC; we
+	# accept it here in order to tolerate that, but reject any
+	# variations.
+	javascript-ghcjs)
+		;;
+	javascript-* | *-ghcjs)
+		echo "Invalid configuration '$1': cpu '$cpu' is not valid with os '$os$obj'" 1>&2
+		exit 1
+		;;
+esac
+
 # As a final step for OS-related things, validate the OS-kernel combination
 # (given a valid OS), if there is a kernel.
 case $kernel-$os-$obj in
diff --git a/doc/config.sub.1 b/doc/config.sub.1
index 60b0a55..7c4777e 100644
--- a/doc/config.sub.1
+++ b/doc/config.sub.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.48.5.
-.TH CONFIG.SUB "1" "August 2023" "GNU config.sub (2023-08-07)" "User Commands"
+.TH CONFIG.SUB "1" "August 2023" "GNU config.sub (2023-08-16)" "User Commands"
 .SH NAME
 config.sub \- validate and canonicalize a configuration triplet
 .SH SYNOPSIS
diff --git a/testsuite/config-sub.data b/testsuite/config-sub.data
index af30cd9..af65330 100644
--- a/testsuite/config-sub.data
+++ b/testsuite/config-sub.data
@@ -343,6 +343,8 @@ isi68						m68k-isi-sysv
 j90						j90-cray-unicos
 j90-cray					j90-cray-unicos
 j90-unicos					j90-cray-unicos
+javascript-ghcjs				javascript-unknown-ghcjs
+javascript-unknown-ghcjs			javascript-unknown-ghcjs
 k1om						k1om-unknown-none
 k1om-linux					k1om-unknown-linux-gnu
 kvx-cos						kvx-unknown-cos