has_many :through across namespace fails

class Person < ActiveRecord::Base
  has_many :manager_roles, :class_name => "Organization::Department"
  has_many :departments, :through => :manager_roles
end

module Organization
  class Department < ActiveRecord::Base
    has_many :manager_roles
  end
  
  class ManagerRole < ActiveRecord::Base
    belongs_to :department
    belongs_to :person
  end
end

has_many :departments, :through => :manager_roles will crash:

NameError: uninitialized constant Person::Department
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/base.rb:1199:in `compute_type'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/reflection.rb:162:in `send'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/reflection.rb:162:in `klass'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/through_association_scope.rb:56:in `construct_joins'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/through_association_scope.rb:11:in `construct_scope'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/has_many_through_association.rb:84:in `find_target'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/association_collection.rb:409:in `load_target'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/association_proxy.rb:145:in `inspect'

We can work around it by changing ManagerRole to specifically declare the class name:

  class ManagerRole < ActiveRecord::Base

belongs_to :department, :class_name => "Organization::Department"
belongs_to :person

  end

It appears that compute_type would need to also search the module of the join model.