diff --git a/debian/changelog b/debian/changelog
index 5707afe1..d0eeb23c 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -7,6 +7,7 @@ livecd-rootfs (24.04.8) UNRELEASED; urgency=medium
   * Remove *-dvd glob handling for live layers; Ubuntu Studio is the only
     remaining "DVD" flavor, and with the move to the new installer this bit
     is also now incorrect.
+  * live-build/auto/config: fail immediately on unknown arch/subarch.
 
  -- Steve Langasek <steve.langasek@ubuntu.com>  Tue, 05 Dec 2023 21:12:26 -0800
 
diff --git a/live-build/auto/config b/live-build/auto/config
index c99ee667..6da42f77 100755
--- a/live-build/auto/config
+++ b/live-build/auto/config
@@ -1,6 +1,24 @@
 #! /bin/sh
 set -e
 
+case $ARCH:$SUBARCH in
+	amd64:|amd64:generic|amd64:intel-iot|\
+	arm64:|arm64:generic|arm64:raspi|arm64:snapdragon|\
+	arm64:tegra|arm64:tegra-igx|arm64:x13s|\
+	armhf:|armhf:raspi|\
+	i386:|\
+	ppc64el:|\
+	riscv64:|riscv64:generic|riscv64:icicle|riscv64:licheerv|\
+	riscv64:nezha|riscv64:unmatched|riscv64:visionfive|riscv64:visionfive2|\
+	s390x:|\
+	*appliance*)
+		;;
+	*)
+		echo "Unknown architecture target $ARCH:$SUBARCH"
+		exit 1
+		;;
+esac
+
 if [ -e config/germinate-output ]; then
             mv -T config/germinate-output germ-tmp
             rm -rf config