diff --git a/live-build/auto/config b/live-build/auto/config
index 3b564467..c2a7f2bd 100755
--- a/live-build/auto/config
+++ b/live-build/auto/config
@@ -1084,7 +1084,7 @@ case $PROJECT in
 		;;
 esac
 
-case "$ARCH+${SUBARCH:-}" in
+case "$ARCH${SUBARCH:++$SUBARCH}" in
 	arm*+raspi)
 		# Common configuration for all Raspberry Pi image variants (server,
 		# desktop etc.)