diff --git a/lib/system/has-flag.js b/lib/system/has-flag.js
index a347dd4..85f176a 100644
--- a/lib/system/has-flag.js
+++ b/lib/system/has-flag.js
@@ -25,7 +25,7 @@ SOFTWARE.
 'use strict';
 
 module.exports = function(flag, argv) {
-  argv = argv || process.argv;
+  argv = argv || process.argv || [];
 
   var terminatorPos = argv.indexOf('--');
   var prefix = /^-{1,2}/.test(flag) ? '' : '--';