Looks like my last patch (#150) introduced a bug where the Rack::Lock mutex wasn't being released. We believe this is fixed in Rack 1.4.1, but as Rails 3.1 is still on Rack 1.3.x, we figured we should handle it here as well.
Fixed a Rack::Lock bug around failing to close the response body
Thank you. It will go in Webmock 1.8.0