googleapis revokeCredentials not returning a result in successful callback

Question

According to the test suite the callback function passed to revokeCredentials gets a result object if the operation was successful which should contain a success property. However, when I use this snippet:

oauth2client.revokeCredentials(function (error, result) {
  if (error || !result.success) {
    console.error('Failed to revoke credentials!');
    console.error(error || result);
  } else {
    //...
  }
});

I get: TypeError: Cannot read property 'success' of undefined - am I missing something?

Copied from issue #445