SimpleCov Not Giving Code Coverage for Watir-Rails Actions

Using Rails 3, SimpleCov (0.9.2) gives me code coverage for all of my tests but fails to give me a report on what my automated Watir-Rails (1.2.1) browser calls in an ActionDispatch::IntegrationTest. Code that is called normally (ie not through Watir) shows up on the coverage fine. I've tried to configure my files like one would with the Selenium webdriver since I've heard that Watir is built on top of that, but that isn't doing the trick. Is there some extra setup I have to do in order to make it all work together?