diff --git a/bin/pegjs b/bin/pegjs
index c24246e..46694e5 100755
--- a/bin/pegjs
+++ b/bin/pegjs
@@ -45,7 +45,7 @@ function abort(message) {
 var args = process.argv.slice(2); // Trim "node" and the script path.
 
 function isOption(arg) {
-  return /-.+/.test(arg);
+  return /^-/.test(arg);
 }
 
 function nextArg() {