Ho to add include polymorphic association to nested association

Question

I have a model with a polymorphic association :

class Poi < ApplicationRecord
  belongs_to :poitable, polymorphic: true, optional: true, dependent: :destroy, touch: true
  belongs_to :master_poi, class_name: 'Poi', optional: true
end


class Course < ApplicationRecord
  belongs_to :poi_start, optional: true, class_name: 'Poi'
  belongs_to :poi_end, optional: true, class_name: 'Poi'.  
  has_many :steps, -> { includes(:poi_start, poi_end: [:services, master_poi: [:services] ])
end

poi_start, poi_end, master_poi are attached to Poi model

I would like to add poitable association to the has_many :steps like :

  has_many :steps, -> { includes(:poi_start, poi_end: [:poitable, :services, master_poi: [:poitable, :services] ])

but get an error "Cannot eagerly load the polymorphic association :poitable"