Required segments in routing


Has anyone an explanation why the following routing is not working?

ActionController::Routing::Routes.draw do |map|
map.namespace :admin do |admin|
admin.connect ‘:controller/:action/:id’
admin.connect ‘:controller/:action/:id.:format’
map.connect ‘:controller/:action/:id’
map.connect ‘:controller/:action/:id.:format’

The following error message ist caused only by “admin.connect
Route segment “:controller” cannot be optional because it precedes a
required segment. This segment will be required.

Replacing it with the following rule works fine:

map.connect ‘admin/users/:action.:format’, { :controller => ‘admin/
users’ }

Interestingly, the variant without explicit format works fine under
the namespace…

Any idea?