diff --git a/script/trees b/script/trees
index 306f189..f224f94 100755
--- a/script/trees
+++ b/script/trees
@@ -24,6 +24,8 @@ mode="all" # make all
 
 main()
 {
+	[ $# -lt 1 ] && $err "No argument provided"
+
 	while getopts f:b:m:u:c:x:s:l:n:d: option; do
 		[ -n "$_f" ] && $err "only one flag is permitted"
 		_f="$1"