i18n-backend-problem

# rake --trace spec
(in /home/alban/share/projects/dryade/stop-area-clustering)
** Invoke spec (first_time)
** Invoke db:test:prepare (first_time)
** Invoke db:abort_if_pending_migrations (first_time)
** Invoke environment (first_time)
** Execute environment
rake aborted!
no such file to load -- i18n/backend
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/vendor/i18n-0.3.7/i18n.rb:32:in `backend'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/vendor/i18n-0.3.7/i18n.rb:131:in `reload!'
/var/lib/gems/1.8/gems/actionpack-2.3.8/lib/action_controller/dispatcher.rb:21:in `define_dispatcher_callbacks'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:182:in `call'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:182:in `evaluate_method'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:166:in `call'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:90:in `run'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:90:in `each'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:90:in `send'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:90:in `run'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:276:in `run_callbacks'
/var/lib/gems/1.8/gems/actionpack-2.3.8/lib/action_controller/dispatcher.rb:51:in `send'
/var/lib/gems/1.8/gems/actionpack-2.3.8/lib/action_controller/dispatcher.rb:51:in `run_prepare_callbacks'
/var/lib/gems/1.8/gems/rails-2.3.8/lib/initializer.rb:631:in `prepare_dispatcher'
/var/lib/gems/1.8/gems/rails-2.3.8/lib/initializer.rb:185:in `process'
/var/lib/gems/1.8/gems/rails-2.3.8/lib/initializer.rb:113:in `send'
/var/lib/gems/1.8/gems/rails-2.3.8/lib/initializer.rb:113:in `run'
/home/alban/share/projects/dryade/stop-area-clustering/config/environment.rb:16