selenium-webdriver threaded script execution fails

script_execute fail

puts '--start'

profile = Selenium::WebDriver::Firefox::Profile.new
driver = Selenium::WebDriver.for :firefox, :profile => profile

timeout = Thread.new(Time.now + 7) do |end_time|
  while Time.now < end_time
    Thread.pass
  end
  puts '--execute'
  puts driver.execute_script("return window.screen.__defineGetter__('height', function(){return 1080;});")
  # at this point stream closes with "error: closed stream" message in console 
end

process = Thread.new do
  driver.navigate.to url
end

process.join
timeout.join

driver.quit

puts '--end'