Issue while trying to exclude articles with specific tag using Rails 5 and polymorphic association

excluding-polymorphic.md

ActiveRecord excluding polymorphic association issue

Considering this situation with Rails 5: I have an Article model and a Tag model. An article has many tags, and a tag can belong to many articles. My schema then looks like this:

class Article < ApplicationRecord
  has_many :taggings, as: :taggable
  has_many :tags, through: :taggings
end

class Tagging < ApplicationRecord
  belongs_to :taggable, polymorphic: true
  belongs_to :tag
end

class Tag < ApplicationRecord
  has_many :taggings, dependent: :destroy
  has_many :articles, through: :taggings, source: :taggable, source_type: 'Article'
end

My goal is to find every article which has not a specific tag (with name "ignore").

ignored_tag_id = Tag.select(:id).find_by(name: 'ignore').id
articles_with_this_tag = Article.joins(:taggings).where.not(taggings: { tag_id: ignore_tag.id })

This successfully excludes every article which includes the tag "ignore", unless this article has another tag. If my article has two tags, including the "ignore" one, it is selected.