Polymorhpic nested forms gotcha

class Project < AR::B
  has_many :comments, :as => :commentable
end
class Comment < AR::B
  belongs_to :commentable
end

- form_for :project do |project_form|
  / fields_for :comment doesn't work :-S
  - project_form.fields_for :comment_attributes do |comment_form|
    = render :partial => "comments/form", :locals => {:f => comment_form}