Preloading polymorphic association doesn't work with namespaced models

Association preload tries to look up included polymorphic models by base_class.sti_name instead of base_class.name, which differs with namespaced models. (sti_name drops the namespace.) BelongsToPolymorphic automatically creates the association with type = base_class.name, so looking it up with base_class.sti_name returns nil.

module Namespace
  class ModelOne
    belongs_to :polymorphic_relationship, :polymorphic => true
  end

  class ModelTwo
    has_one :model_one, :as => :polymorphic_relationship
  end
end

model_two = Namespace::ModelTwo.create(:id => 1)
model_one = Namespace::ModelOne.create(:id => 1, :polymorphic_relationship => model_two)

model_two = Namespace::ModelTwo.find_by_id(1)
model_two.model_one # (is present)

model_two = Namespace::ModelTwo.find_by_id(1, :include => :model_one)
model_two.model_one # (is nil)

Attached is a patch to AssociationPreload to fix this.