diff --git a/lib/jison.js b/lib/jison.js
index d078056ee..876b3a2fc 100755
--- a/lib/jison.js
+++ b/lib/jison.js
@@ -1280,7 +1280,12 @@ function commonjsMain (args) {
         console.log('Usage: '+args[0]+' FILE');
         process.exit(1);
     }
-    var source = require('fs').readFileSync(require('path').normalize(args[1]), "utf8");
+    var source = '';
+    var fs = require('fs');
+    var path = require('path');
+    if (typeof fs !== 'undefined' && fs !== null && typeof path !== 'undefined' && path !== null) {
+        source = fs.readFileSync(path.normalize(args[1]), "utf8");
+    }
     return exports.parser.parse(source);
 }