diff --git a/hack/tfw.sh b/hack/tfw.sh
index 96e1210..8474a43 100755
--- a/hack/tfw.sh
+++ b/hack/tfw.sh
@@ -128,7 +128,7 @@ start_test()
     wait
 }
 
-case $1 in
+case ${1:-} in
     buildtfw)
         build_baseimage
     ;;