diff --git a/lib/adapters/xhr.js b/lib/adapters/xhr.js
index 2615c10..21badcf 100644
--- a/lib/adapters/xhr.js
+++ b/lib/adapters/xhr.js
@@ -8,6 +8,7 @@ var buildURL = require('./../helpers/buildURL');
 var parseHeaders = require('./../helpers/parseHeaders');
 var transformData = require('./../helpers/transformData');
 var isURLSameOrigin = require('./../helpers/isURLSameOrigin');
+var btoa = window.btoa || require('./../helpers/btoa.js')
 
 module.exports = function xhrAdapter(resolve, reject, config) {
   // Transform request data
@@ -41,9 +42,9 @@ module.exports = function xhrAdapter(resolve, reject, config) {
 
   // HTTP basic authentication
   if (config.auth) {
-    requestHeaders['Authorization'] = 'Basic: ' + window.btoa(username + ':' + password);
     var username = config.auth.username || '';
     var password = config.auth.password || '';
+    requestHeaders['Authorization'] = 'Basic: ' + btoa(username + ':' + password);
   }
 
   // Create the request
diff --git a/test/specs/basicAuth.spec.js b/test/specs/basicAuth.spec.js
index 4816e43..0aae6b5 100644
--- a/test/specs/basicAuth.spec.js
+++ b/test/specs/basicAuth.spec.js
@@ -1,6 +1,6 @@
 var axios = require('../../index');
 
-describe('options', function () {
+describe('basicAuth without btoa polyfill', function () {
   beforeEach(function () {
     jasmine.Ajax.install();
   });
@@ -9,66 +9,7 @@ describe('options', function () {
     jasmine.Ajax.uninstall();
   });
 
-  it('should accept HTTP Basic auth with user/pass', function (done) {
-    var request;
-
-    axios({
-      url: '/foo',
-      auth: {
-        user: 'Aladdin',
-        pass: 'open sesame'
-      }
-    });
-
-    setTimeout(function () {
-      request = jasmine.Ajax.requests.mostRecent();
-
-      expect(request.requestHeaders['Authorization']).toEqual('Basic: QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
-      done();
-    }, 0);
-  });
-
-  it('should accept HTTP Basic auth with username/pass', function (done) {
-    var request;
-
-    axios({
-      url: '/foo',
-      auth: {
-        username: 'Aladdin',
-        pass: 'open sesame'
-      }
-    });
-
-    setTimeout(function () {
-      request = jasmine.Ajax.requests.mostRecent();
-
-      expect(request.requestHeaders['Authorization']).toEqual('Basic: QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
-      done();
-    }, 0);
-  });
-
-  it('should accept HTTP Basic auth with user/password', function (done) {
-    var request;
-
-    axios({
-      url: '/foo',
-      auth: {
-        user: 'Aladdin',
-        password: 'open sesame'
-      }
-    });
-
-    setTimeout(function () {
-      request = jasmine.Ajax.requests.mostRecent();
-
-      expect(request.requestHeaders['Authorization']).toEqual('Basic: QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
-      done();
-    }, 0);
-  });
-
   it('should accept HTTP Basic auth with username/password', function (done) {
-    var request;
-
     axios({
       url: '/foo',
       auth: {
@@ -78,10 +19,25 @@ describe('options', function () {
     });
 
     setTimeout(function () {
-      request = jasmine.Ajax.requests.mostRecent();
+      var request = jasmine.Ajax.requests.mostRecent();
 
       expect(request.requestHeaders['Authorization']).toEqual('Basic: QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
       done();
     }, 0);
   });
+
+  it('should fail to encode HTTP Basic auth credentials with non-Latin1 characters', function (done) {
+    axios({
+      url: '/foo',
+      auth: {
+        username: 'Aladßç£☃din',
+        password: 'open sesame'
+      }
+    }).then(function(response) {
+      done(new Error('Should not succeed to make a HTTP Basic auth request with non-latin1 chars in credentials.'))
+    }).catch(function(error) {
+      expect(error.message).toEqual('INVALID_CHARACTER_ERR: DOM Exception 5')
+      done()
+    });
+  });
 });
diff --git a/test/specs/basicAuthWithPolyfill.spec.js b/test/specs/basicAuthWithPolyfill.spec.js
new file mode 100644
index 0000000..83aaf9b
--- /dev/null
+++ b/test/specs/basicAuthWithPolyfill.spec.js
@@ -0,0 +1,52 @@
+var axios = require('../../index');
+
+describe('basicAuth with btoa polyfill', function () {
+  beforeAll(function() {
+    this.original_btoa = window.btoa;
+    window.btoa = undefined;
+  })
+
+  afterAll(function() {
+    window.btoa = this.original_btoa;
+  })
+
+  beforeEach(function () {
+    jasmine.Ajax.install();
+  });
+
+  afterEach(function () {
+    jasmine.Ajax.uninstall();
+  });
+
+  it('should accept HTTP Basic auth with username/password', function (done) {
+    axios({
+      url: '/foo',
+      auth: {
+        username: 'Aladdin',
+        password: 'open sesame'
+      }
+    });
+
+    setTimeout(function () {
+      var request = jasmine.Ajax.requests.mostRecent();
+
+      expect(request.requestHeaders['Authorization']).toEqual('Basic: QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
+      done();
+    }, 0);
+  });
+
+  it('should fail to encode HTTP Basic auth credentials with non-Latin1 characters', function (done) {
+    axios({
+      url: '/foo',
+      auth: {
+        username: 'Aladßç£☃din',
+        password: 'open sesame'
+      }
+    }).then(function(response) {
+      done(new Error('Should not succeed to make a HTTP Basic auth request with non-latin1 chars in credentials.'))
+    }).catch(function(error) {
+      expect(error.message).toEqual('\'btoa\' failed: The string to be encoded contains characters outside of the Latin1 range.')
+      done()
+    });
+  });
+});