diff --git a/lib/client.js b/lib/client.js
index 98344b2..88b2926 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -44,6 +44,9 @@ function Client(config) {
       tokenHost: config.tokenHost,
       tokenPath: config.tokenPath,
     },
+    options: {
+      authorizationMethod: 'body'
+    },
     http: {
       headers: {
         'User-Agent': UpworkLibraryUserAgent
@@ -139,8 +142,7 @@ Client.prototype.setAccessToken = function(callback) {
 
   if (aToken.expired()) {
     debug('the access token has expired, refreshing');
-    aToken.refresh((error, result) => {
-      aToken = result;
+    aToken.refresh().then((aToken) => {
       debug(aToken, 'received a new AccessToken object');
       this.config.accessToken = aToken.token.access_token;
       callback(aToken.token);