diff --git a/build-docker.sh b/build-docker.sh
index 7ba3194..350f722 100755
--- a/build-docker.sh
+++ b/build-docker.sh
@@ -74,8 +74,14 @@ fi
 BUILD_OPTS="$(echo "${BUILD_OPTS:-}" | sed -E 's@\-c\s?([^ ]+)@-c /config@')"
 
 # Check the arch of the machine we're running on. If it's 64-bit, use a 32-bit base image instead
-ARCH=$(uname -m)
-[[ $ARCH == "x86_64" || $ARCH == "aarch64" ]] && BASE_IMAGE=i386/debian:buster || BASE_IMAGE=debian:buster
+case "$(uname -m)" in
+  x86_64|aarch64)
+    BASE_IMAGE=i386/debian:buster
+    ;;
+  *)
+    BASE_IMAGE=debian:buster
+    ;;
+esac
 ${DOCKER} build --build-arg BASE_IMAGE=${BASE_IMAGE} -t pi-gen "${DIR}"
 
 if [ "${CONTAINER_EXISTS}" != "" ]; then