Single Table Inheritance and has_many_and_belongs_to

Question

I use single table inheritance like this:

class Reservation < ApplicationRecord
end

class Stay < Reservation
end

Now I've got another class called room and I want it to be in many-to-many relation with the stay because reservation is more general. Moreover I don't need the association model so I want to use has_many_and_belongs to. So I created stay_rooms table:

class CreateStayRooms < ActiveRecord::Migration[5.1]
  def change
    create_table :stay_rooms, id: false do |t|
      t.references :reservation, foreign_key: true, index: true
      t.references :room, foreign_key: true, index: true
    end
  end
end

and prepared models:

class Stay < Reservation
  has_and_belongs_to_many :rooms,
    join_table: :stay_rooms
end

class Room < ApplicationRecord
  has_and_belongs_to_many :stays, 
    class_name: 'Stay', 
    join_table: :stay_rooms
end

But it doesn't work and I keep getting "ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: stay_rooms.stay_id" when I try simple query: Stay.first.rooms. So I checked the docs and added foreign_key and association_key like this:

class Stay < Reservation
  has_and_belongs_to_many :rooms,
    foreign_key: 'room_id',  
    association_foreign_key: 'room_id',
    join_table: :stay_rooms
end

class Room < ApplicationRecord
  has_and_belongs_to_many :stays, 
    class_name: 'Stay', 
    foreign_key: 'reservation_id', 
    association_foreign_key: 'reservation_id',
    join_table: :stay_rooms
end

But it still didn't make it work and I don't know how to solve it.

UPDATE

I had a typo I mispelled foreign key and after correcting it it works but only one way. I can get rooms associated with stay but when I do it another way around it gives me an empty collection despite the fact I've got a room associated with a stay. (I did Stay.first.rooms << Room.first)