qemu-start: do not always overwrite ISO envvar

1 files changed, 1 insertions, 1 deletions

diff --git a/qemu-start b/qemu-start
index ff9b62a..323df4b 100755
--- a/qemu-start
+++ b/qemu-start
@@ -16,7 +16,7 @@ ISO=*.iso)
 	;;
 esac
 
-: ${ISO=/usr/share/virtualbox/ubuntu-12.04.1-desktop-amd64.iso}
+ISO=${ISO-/usr/share/virtualbox/ubuntu-12.04.1-desktop-amd64.iso}
 case $ISO in
 *.iso)
 	set -- -cdrom "$ISO" "$@"