cache_key timestamp not calculated when using offset

cache_key_test.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', github: 'rails/rails'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.timestamps
  end
end

class Post < ActiveRecord::Base
end

class BugTest < Minitest::Test
  def test_cache_key
    10.times { Post.create! }

    cache_key1 = Post.limit(5).cache_key
    cache_key2 =  Post.limit(5).offset(5).cache_key

    puts cache_key1
    puts cache_key2
  end
end