Engine controllers are read twice

In all our engines, the app/controllers/*_controller.rb are read twice
during application startup, resulting in undesirable side effects,
such as duplicated before and after filters.

We have post a ticket in the Rails Engine tracking system [1], but we
are doubting if it is also reasonable to post it in Rails Trac,
because, althought de engine has its own controllers, filters are
Rails features.

The question is: who causes the filters be read twice?

[1] http://dev.rails-engines.org/tickets/177