diff --git a/lib/adapters/xhr.js b/lib/adapters/xhr.js
index eb7fe18..9022236 100644
--- a/lib/adapters/xhr.js
+++ b/lib/adapters/xhr.js
@@ -5,7 +5,7 @@ var buildURL = require('./../helpers/buildURL');
 var parseHeaders = require('./../helpers/parseHeaders');
 var transformData = require('./../helpers/transformData');
 var isURLSameOrigin = require('./../helpers/isURLSameOrigin');
-var btoa = window && window.btoa || require('./../helpers/btoa');
+var btoa = (typeof window !== 'undefined' && window.btoa) || require('./../helpers/btoa');
 
 module.exports = function xhrAdapter(resolve, reject, config) {
   var requestData = config.data;
@@ -22,7 +22,7 @@ module.exports = function xhrAdapter(resolve, reject, config) {
   // For IE 8/9 CORS support
   // Only supports POST and GET calls and doesn't returns the response headers.
   // DON'T do this for testing b/c XMLHttpRequest is mocked, not XDomainRequest.
-  if (process.env.NODE_ENV !== 'test' && window.XDomainRequest && !('withCredentials' in request) && !isURLSameOrigin(config.url)) {
+  if (process.env.NODE_ENV !== 'test' && typeof window !== 'undefined' && window.XDomainRequest && !('withCredentials' in request) && !isURLSameOrigin(config.url)) {
     request = new window.XDomainRequest();
     loadEvent = 'onload';
     xDomain = true;