diff --git a/mclevel b/mclevel
index eae04ce..ee7d55d 100755
--- a/mclevel
+++ b/mclevel
@@ -111,6 +111,7 @@ main() {
 			error "Too many arguments: $arg" 2
 		fi
 	done
+	[ -z "$_level" ] && error "Program requires argument" 2
 	[ -n "$_opthelp" ] && printhelp && exit 0
 	givelevels "$_level"
 }