webdriverio + mocha issue

testme.js

// run with: ./node_modules/.bin/mocha --timeout 99999 testme.js
var webdriverio = require('webdriverio'),
    mocha       = require('mocha'),
    url         = "http://google.com";

var client = webdriverio.remote(
    {
        desiredCapabilities: {browserName: 'chrome'}
    }
);

client.addCommand('custom', function(cb) {
    return this.url(url)
        .pause(5000)
        .waitUntil(function() {
            console.log('returning true');
            return (1 + 1 == 2);
        }, 5000)
        .addValue('.gsfi', 'test')
        .click("input[name='btnI']");
});

describe('test', function() {
    before(function(done){
        client.init(done);
    });

    it('should work', function(done) {
        client
            .custom()
            // this is invoked immediately instead of waiting for custom to return:
            .waitForVisible('#nonexistent', 5000).then(function(el) {
                console.log('non existent exists!'); // how is this logging?!?!?!?!
            });
    });

    after(function(done) {
        client.end(done);
    });
});