I am porting a 2.x rails app to rails3; we'll call it foo-app. Foo-app is one section of a larger rails app and lives at main_rails_app.com/foo-app. Previously we just set up the following in our foo-app production config to ensure that our foo-app routes worked properly: ActionController::Base.relative_url_root = "/foo-app" However, with rails3, I now get: DEPRECATION WARNING: ActionController::B