Observer and uninitialized constant

Hello,

I have an application running on rails 1.2.3
I use act_as_authenticated and i want to add an observer on the users
table.

my environment.rb file :

config.active_record.observers = :user_observer

I have created an user_observer.rb file in the model folder like this :
class UserObserver < ActiveRecord::Observer

def after_save(user)
Notifications.deliver_user(“@*.com”, “Modification on the
account”, user)
end

end

When i update a user entry, i have a crash and the following message in
production.log file :

NameError (uninitialized constant UserObserver::Notifications):
/usr/local/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:477:in
const_missing' /app/models/user_observer.rb:5:inafter_save’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/observer.rb:154:in
send' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/observer.rb:154:inupdate’
/usr/local/lib/ruby/1.8/observer.rb:185:in notify_observers' /usr/local/lib/ruby/1.8/observer.rb:184:ineach’
/usr/local/lib/ruby/1.8/observer.rb:184:in notify_observers' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/callbacks.rb:364:innotify’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/callbacks.rb:328:in
callback' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/callbacks.rb:243:increate_or_update’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1545:in
save_without_validation' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/validations.rb:752:insave_without_transactions’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:129:in
save' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/connection_adapters/abstract/database_statements.rb:59:intransaction’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:95:in
transaction' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:121:intransaction’
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:129:in
save' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1592:inupdate_attributes’
/app/controllers/account_controller.rb:79:in update' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/base.rb:1095:insend’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/base.rb:1095:in
perform_action_without_filters' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:632:incall_filter’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:638:in
call_filter' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:438:incall’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:637:in
call_filter' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:638:incall_filter’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:438:in
call' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:637:incall_filter’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:619:in
perform_action_without_benchmark' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/benchmarking.rb:66:inperform_action_without_rescue’
/usr/local/lib/ruby/1.8/benchmark.rb:293:in measure' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/benchmarking.rb:66:inperform_action_without_rescue’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/rescue.rb:83:in
perform_action' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/base.rb:430:insend’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/base.rb:430:in
process_without_filters' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/filters.rb:624:inprocess_without_session_management_support’
/usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/session_management.rb:114:in
process' /usr/local/lib/ruby/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/base.rb:330:inprocess’
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/dispatcher.rb:41:in
dispatch' /usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:168:inprocess_request’
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:143:in
process_each_request!' /usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:109:inwith_signal_handler’
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:142:in
process_each_request!' /usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.7/lib/fcgi.rb:612:ineach_cgi’
/usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.7/lib/fcgi.rb:609:in
each' /usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.7/lib/fcgi.rb:609:ineach_cgi’
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:141:in
process_each_request!' /usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:55:inprocess!’
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/fcgi_handler.rb:25:in
`process!’
dispatch.fcgi:24

Have you an idea ?
Thanks,