Ruby-on-rails – has_many while respecting build strategy in factory_girl

Situation

# Models
class User < ActiveRecord::Base
  has_many :items 
end 

class Items < ActiveRecord::Base
  belongs_to :user 
  validates_presence_of :user_id 
end 

# Factories
Factory.define(:user) do |u| 
  u.name "foo" 
end 

Factory.define(:user_with_items, :parent => :user) do |u| 
  u.items {|items| [items.association(:item), items.association(:item)]} 
end

Factory.define(:item) do |i| 
  i.color "red" 
end 

Factory.define(:item_with_user, :parent => :user) do |i| 
  i.association(:user) 
end

Problem

If you run @user = Factory(:user_with_items) then @user.items contains the two items. The issue is that the items aren't associated with the user in the database. If you reload the association @user.items(true) then you get back an empty array. I know you can build them
manually or create helper methods on your own to build the object graph, but I'd like to avoid that.

Question

So, my question is how can you build up a has_many relationship in factory_girl while respecting the build strategy?