diff --git a/src/boot.sh b/src/boot.sh
index e8449c4..7affa66 100644
--- a/src/boot.sh
+++ b/src/boot.sh
@@ -33,10 +33,8 @@ case "${BOOT_MODE,,}" in
     BOOT_OPTS="-rtc base=localtime"
     ;;
   *)
-    info "Unknown boot mode '${BOOT_MODE}', defaulting to 'uefi'"
-    BOOT_MODE="uefi"
-    ROM="AAVMF_CODE.no-secboot.fd"
-    VARS="AAVMF_VARS.fd"
+    error "Unrecognized BOOT_MODE, value \"${BOOT_MODE}\" is not recognized!"
+    exit 33
     ;;
 esac