acts_as_taggable_on Gem not working for Rails 5

I made a rails application and added the acts-as-taggable-on gem, ran the rake db:migrate and added the field to Article.rb. I seem to get this error with a rail 5.1 app. I can't figure out what it is.

GemFile

gem 'acts-as-taggable-on', '~> 4.0'

Article.rb

class Article < ApplicationRecord
    include TheComments::Commentable

     acts_as_taggable_on :tags

        belongs_to :user

      # Denormalization methods
      # Check the documentation for information on advanced usage
        def commentable_title
        title
      end

      def commentable_url
        ['', self.class.to_s.tableize, id].join('/')
      end

      def commentable_state
        :published.to_s
      end
    end

However I get this error:

Running via Spring preloader in process 18395
Loading development environment (Rails 5.1.2)
2.4.0-rc1 :001 > Article
NoMethodError: undefined method `acts_as_taggable_on' for Article (call 'Article.connection' to establish a connection):Class
    from app/models/article.rb:6:in `<class:Article>'
    from app/models/article.rb:1:in `<top (required)>'
    from (irb):1
2.4.0-rc1 :002 > Article
NoMethodError: undefined method `acts_as_taggable_on' for Article (call 'Article.connection' to establish a connection):Class
    from app/models/article.rb:6:in `<class:Article>'
    from app/models/article.rb:1:in `<top (required)>'

The reason for the issue is with the version of the gem. The version of the gem that you are using doesn't support Rails 5.

You can resolve your error by pulling the gem from direct from the github. For that just use below code in your gemfile:

gem 'acts-as-taggable-on', :git => 'https://github.com/mbleigh/acts-as-taggable-on'