diff --git a/src/backends/github/AuthenticationPage.js b/src/backends/github/AuthenticationPage.js
index f9e0f2c7..b3d62588 100644
--- a/src/backends/github/AuthenticationPage.js
+++ b/src/backends/github/AuthenticationPage.js
@@ -13,12 +13,11 @@ export default class AuthenticationPage extends React.Component {
 
   handleLogin = (e) => {
     e.preventDefault();
-    let auth;
-    if (document.location.host.split(':')[0] === 'localhost') {
-      auth = new Authenticator({ site_id: 'cms.netlify.com' });
-    } else {
-      auth = new Authenticator({ site_id: this.props.siteId });
+    const cfg = {
+      base_url: this.props.base_url,
+      site_id: (document.location.host.split(':')[0] === 'localhost') ? 'cms.netlify.com' : this.props.siteId
     }
+    const auth = new Authenticator(cfg);
 
     auth.authenticate({ provider: 'github', scope: 'repo' }, (err, data) => {
       if (err) {
diff --git a/src/containers/App.js b/src/containers/App.js
index 0b6cfed8..6f4d62f9 100644
--- a/src/containers/App.js
+++ b/src/containers/App.js
@@ -89,6 +89,7 @@ class App extends React.Component {
             error: auth && auth.get('error'),
             isFetching: auth && auth.get('isFetching'),
             siteId: this.props.config.getIn(["backend", "site_domain"]),
+            base_url: this.props.config.getIn(["backend", "base_url"], null)
           })
         }
       </div>