diff --git a/lib/user-methods.js b/lib/user-methods.js
index 4035bc85..d4cbe209 100644
--- a/lib/user-methods.js
+++ b/lib/user-methods.js
@@ -132,18 +132,19 @@ function _authenticate(userConstructor, server, json, callback) {
         headers: postHeaders,
         open_timeout: 5000
     };
+
     const promise = performFetch(url, options)
         .then((response) => {
             if (response.status !== 200) {
-                return response.json().then((body) => callback(new AuthError(body)));
+                return response.json().then((body) => Promise.reject(new AuthError(body)));
             } else {
                 return response.json().then(function (body) {
                     // TODO: validate JSON
                     const token = body.refresh_token.token;
                     const identity = body.refresh_token.token_data.identity;
                     const isAdmin = body.refresh_token.token_data.is_admin;
-                    callback(undefined, userConstructor.createUser(server, identity, token, false, isAdmin));
-                })
+                    return userConstructor.createUser(server, identity, token, false, isAdmin);
+                });
             }
         });
 
@@ -193,8 +194,8 @@ const staticMethods = {
                 const message = "register(..., callback) is now deprecated in favor of register(): Promise<User>. This function argument will be removed in future versions.";
                 (console.warn || console.log).call(console, message);
             }
-            _authenticate(this, server, json, callback);
-            
+           
+            return _authenticate(this, server, json, callback);
         },
 
         login(server, username, password, callback) {
@@ -209,7 +210,8 @@ const staticMethods = {
                 const message = "login(..., callback) is now deprecated in favor of login(): Promise<User>. This function argument will be removed in future versions.";
                 (console.warn || console.log).call(console, message);
             }
-            _authenticate(this, server, json, callback);
+
+            return _authenticate(this, server, json, callback);
         },
 
         registerWithProvider(server, options, callback) {
@@ -240,7 +242,8 @@ const staticMethods = {
                 const message = "registerWithProvider(..., callback) is now deprecated in favor of registerWithProvider(): Promise<User>. This function argument will be removed in future versions.";
                 (console.warn || console.log).call(console, message);
             }
-            _authenticate(this, server, json, callback);
+            
+            return _authenticate(this, server, json, callback);
         },
 
         _refreshAccessToken: refreshAccessToken