diff --git a/lib/6to5/browser.js b/lib/6to5/browser.js
index 65dc3f64be..a8e946c859 100644
--- a/lib/6to5/browser.js
+++ b/lib/6to5/browser.js
@@ -12,7 +12,7 @@ transform.load = function (url, callback, opts, hold) {
   opts = opts || {};
   opts.filename = opts.filename || url;
 
-  var xhr = window.ActiveXObject ? new window.ActiveXObject("Microsoft.XMLHTTP") : new window.XMLHttpRequest();
+  var xhr = global.ActiveXObject ? new global.ActiveXObject("Microsoft.XMLHTTP") : new global.XMLHttpRequest();
   xhr.open("GET", url, true);
   if ("overrideMimeType" in xhr) xhr.overrideMimeType("text/plain");
 
@@ -60,7 +60,7 @@ var runScripts = function () {
     }
   };
 
-  var _scripts = window.document.getElementsByTagName("script");
+  var _scripts = global.document.getElementsByTagName("script");
   for (var i in _scripts) {
     var _script = _scripts[i];
     if (types.indexOf(_script.type) >= 0) scripts.push(_script);
@@ -73,8 +73,8 @@ var runScripts = function () {
   exec();
 };
 
-if (window.addEventListener) {
-  window.addEventListener("DOMContentLoaded", runScripts, false);
-} else {
-  window.attachEvent("onload", runScripts);
+if (global.addEventListener) {
+  global.addEventListener("DOMContentLoaded", runScripts, false);
+} else if (global.attachEvent) {
+  global.attachEvent("onload", runScripts);
 }