diff --git a/scripts/gen_image_generic.sh b/scripts/gen_image_generic.sh
index 53f73dc6e1..8091d95575 100755
--- a/scripts/gen_image_generic.sh
+++ b/scripts/gen_image_generic.sh
@@ -1,10 +1,10 @@
 #!/usr/bin/env bash
 # Copyright (C) 2006-2012 OpenWrt.org
 set -e -x
-[ $# == 5 -o $# == 6 ] || {
+if [ $# -ne 5 ] && [ $# -ne 6 ]; then
     echo "SYNTAX: $0 <file> <kernel size> <kernel directory> <rootfs size> <rootfs image> [<align>]"
     exit 1
-}
+fi
 
 OUTPUT="$1"
 KERNELSIZE="$2"