Preload association when called from model's method

Suppose I have this simple app working :

# model
class Project
    has_many :numbers

  def my_numbe开发者_开发知识库rs
    numbers
  end
end

# controller
class ProjectController
  def index
    @projects = Project.includes(:numbers)
  end  
end

Within my first view, no problem. I'm calling the association directly, so all numbers have already been loaded.

@projects.each do |project|
  project.numbers
  # no probleme here. Hit the cache of included numbers.
end

And here is the log

Project Load (0.8ms)  SELECT "projects".* FROM "projects" 
ProjectNumber Load (0.5ms)  SELECT "project_numbers".* FROM "project_numbers" WHERE "project_numbers"."project_id" IN (1,2)

But with this second example, calling numbers from within a method call in Project, each call to my_numbers triggers a new db call, as you can see below:

@projects.each do |project|
  project.my_numbers
end

And here is the log

Project Load (0.8ms)  SELECT "projects".* FROM "projects" 
ProjectNumber Load (0.5ms)  SELECT "project_numbers".* FROM "project_numbers" WHERE "project_numbers"."project_id" IN (1,2)
ProjectNumber Load (0.5ms)  SELECT "project_numbers".* FROM "project_numbers" WHERE "project_numbers"."project_id" = 1
ProjectNumber Load (0.5ms)  SELECT "project_numbers".* FROM "project_numbers" WHERE "project_numbers"."project_id" = 2

Is there anyway to avoid that? Why does my model not reusing the included numbers from the first db request?

Thanks in advance!

I have tried this code in Rails 3.0.9 and it does not do the behavior you describe. Are you sure Numbers are not triggering a callback?