configuring castle monorail to not show any extensions

how can I configure Castle Monorail to not have any extensions? I lo开发者_如何学Pythonoked at the documentation and have confugred it's defaultUrlExtension to blank and have also configured it to not use extensions but I'm still getting .castle extension on the urls. What am I missing ? thanks in advance.

public void MonoRail_Configure(IMonoRailConfiguration configuration)
{
  configuration.UrlConfig.UseExtensions = false;
}