Undefined method `namespace 'for main: Object (NoMethodError) - active record / rakefile

I am trying to run a basic Sinatra application. When I get to the rackup stage, I get an error:

/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.1/lib/active_record/railties/databases.rake:3:in `<top (required)>': undefined method `namespace' for main:Object (NoMethodError)

Seems to be a Rake issue. I had no luck finding an answer and I'm not really sure what needs to be fixed. I did update all my gems in the hopes that this helps to no avail. Here is my code that might contribute ...

    rakefile.rb
       require "./frank"
       require "sinatra/activerecord/rake"

    config.ru
        require_relative 'frank'
        map('/welcomes') { run WelcomesController }

    frank.rb
        require 'sinatra/base'
        require 'active_record'
        require 'bcrypt'

        Dir.glob('./{controllers,models}/*rb').each { |file| require file }

        ENV['SINATRA_ENV'] ||= 'development'

        ActiveRecord::Base.establish_connection(
            :adapter => 'sqlite3',
            :database => "db/#{ENV['SINATRA_ENV']}.sqlite"
        )

    spec_helper.rb
        ENV['SINATRA_ENV'] = 'test'
        require_relative '../frank'
        require 'capybara'
        require 'database_cleaner'
        Capybara.app = Rack::Builder.parse_file(File.expand_path('../../config.ru',__FILE__)).first
    RSpec.configure do |config|
        config.include Capybara::DSL
        config.before(:suite) do
            DatabaseCleaner.clean_with(:truncation)
    end
    config.before(:each) do
          DatabaseCleaner.strategy = :transaction
    end
    config.before(:each) do
          DatabaseCleaner.start
    end
    config.after(:each) do
        DatabaseCleaner.clean
    end
end

      

        
        
        
      

    

Many thanks:)

This is below the primary error:

    from /Users/stephaniedean/.rvm/gems/ruby-2.2.1/gems/sinatra-activerecord-2.0.6/lib/sinatra/activerecord/rake.rb:1:in `load'
    from /Users/stephaniedean/.rvm/gems/ruby-2.2.1/gems/sinatra-activerecord-2.0.6/lib/sinatra/activerecord/rake.rb:1:in `<top (required)>'

      

        
        
        
      

    

So it looks like sinatra-activerecord not only activerecord. I tried activerecord 3.2.17 which didn't work. Thanks for the suggestions.