Rails 3 observers

Rails Guides says:
...the UserObserver ... would be saved as app/models/user_observer.rb
and registered in config/environment.rb this way:
config.active_record.observers = :user_observer

But the observer registration above doesn't work because there is no
'config'. For now, I've put it in the config/environments/[APP_ENV].rb
but that seems really sloppy and redundant.

What am I missing here?

Thanks....

If you are using rails 3 the configuration goes in the application.rb file in the config folder. Look at line 23.