Selenium bug in Python PhantomJS webdriver

test.py

import unittest

from selenium import webdriver
from selenium.webdriver.common.keys import Keys

from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support import expected_conditions
from selenium.common.exceptions import TimeoutException

def wait_for_alert(driver):
    browser = driver()

    browser.get('http://www.google.com')
    try:
        WebDriverWait(browser, 2).until(expected_conditions.alert_is_present(),
                                       'Timed out waiting for alert')
    except TimeoutException:
        print("ok!")
    finally:
        browser.quit()

if __name__=='__main__':
    wait_for_alert(webdriver.Firefox)
    wait_for_alert(webdriver.PhantomJS)