watir-webdriver error using chrome browser

watir-webdriver error using chrome browser

I am using watir-webdriver and are getting this error message when opening
a chrome browser:
C:\chromeDriver>irb
DL is deprecated, please use Fiddle
irb(main):001:0> require "watir-webdriver"
=> true
irb(main):002:0> a = Watir::Browser.new (:chrome)
Started ChromeDriver
port=9515
version=0.8
log=C:\chromeDriver\chromedriver.log
Selenium::WebDriver::Error::UnknownError: unknown error: unrecognized
chrome option:
detach
(Driver info: chromedriver=0.8,platform=Windows NT 6.2 x86_64)
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/response.rb:51:in
`assert_ok'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/response.rb:15:in
`initialize'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/http/common.rb:59:in
`new'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/http/common.rb:59:in
`create_response'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/http/default.rb:66:in
`request'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/http/common.rb:40:in
`call'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/bridge.rb:629:in
`raw_execute'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/bridge.rb:98:in
`create_session'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/remote/bridge.rb:68:in
`initialize'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/chrome/bridge.rb:29:in
`initialize'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/common/driver.rb:37:in
`new'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver/common/driver.rb:37:in
`for'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.33.0/lib/selenium/webdriver.rb:67:in
`for'
from
C:/Ruby200/lib/ruby/gems/2.0.0/gems/watir-webdriver-0.6.4/lib/watir-webd
river/browser.rb:46:in `initialize'
from (irb):2:in `new'
from (irb):2
Environment:
Windows 8
Ruby version = ruby 2.0.0p247 (2013-06-27) [i386-mingw32]