Uninitialized constant Model1::Model2::Model3

I am getting uninitialized constant Project::Forum::Topic at
app/controllers/home_controller.rb:46:in `discussions’

I have code below and I am converting from rails 2.3.x to rails 3.2.11,
I am thinking something wrong in routes setting.

Any Idea How can I fix?

models

Project < ActiveRecord::Base
  # Relations under project model
  has_many :features, :dependent => :destroy
  has_many :forums, :class_name=>'Forum::Forum'
  has_many :topics, :class_name=>'Forum::Topic', :through=>:forums

Forum::Forum < Feature
  # Relations under forum model
  has_many :topics, :class_name => 'Forum::Topic', :dependent =>

:destroy

Feature < ActiveRecord::Base
  # Relations under feature model
  belongs_to :project

Forum::Topic < ActiveRecord::Base
   # Relations under topic model
   belongs_to :forum, :foreign_key => :forum_id, :class_name =>

‘Forum::Forum’, :include => :project

home_controller.rb

def discussions
  @project ||= Project.find_by_name 'help'
  @forums = @project.forums
  @topics = @project.topics.recent # HERE I AM GETTING ERRORS
end

routes.rb

scope :home, :controller => "home", :activity => 'read' do
 get :discussions, :path => '/forums', :service_type => 'public'
 get :forums, :action => "discussions"
end

errors
uninitialized constant Project::Forum::Topic
app/controllers/home_controller.rb:46:in `discussions’

yes, those are in “app/models/forum”, it is working fine with Rails
2.3.11