Join 3 tables in Sequel ORM

My models are:

class User < Sequel::Model
 one_to_many :tweets
end

class Tweet < Sequel::Model
  many_to_one :user
  one_to_many :hashtags
end

class Hashtag < Sequel::Model
  many_to_one :tweet
end

What I am looking for is using 'User.hashtags'. I have tried adding

class Hashtag < Sequel::Model
  many_to_one :tweet
  many_to_one :user
end

class User < Sequel::Model
 one_to_many :tweets
 one_to_many :hashtags
end

But this requires me to have a user_id in the hashtag table. My current schema stores hashtags with tweet_id only.

Is there a one_through_many configuration, joining the User => Tweet => Hashtag tables? With the tweet table have the user_id.

Or do I need to add a user_id column to the hashtag table?