Mongoid: Caching Eager Loaded Documents

We have this code: ``` class Band include Mongoid::Document has_many :albums end class Album include Mongoid::Document belongs_to :band end @bands = Band.includes(:albums).entries ``` This is great because now I can run `@bands.first.albums` without hitting the DB. But now, if we write this includes to the rails cache... ``` Rails.cache.write('bands', @bands) ``` ...we then read the cache. ``` bands = Rails.cache.read('bands') ``` This returns an array of band documents... `[#<Band _id: 536a53c969702d208f240000, created_at: 2014-05-07 15:39:53 UTC, updated_at: 2014-05-08 15:55:29 UTC, name: "Pink Floyd", fan_count: 394857, #<Band _id: 536adf2a69702d1574130000, created_at: 2014-05-08 01:34:34 UTC, updated_at: 2014-05-08 01:35:40 UTC, name: "Tool", fan_count: 2958394, #<Band _id: 536bcad169702d743e1e0000, created_at: 2014-05-08 18:20:01 UTC, updated_at: 2014-05-08 18:27:10 UTC, name: "My Morning Jacket", fan_count: 3945734]` ...and then we can't get the albums. ``` bands.first.albums NoMethodError: undefined method 'albums' for #<Array:0x00000104df50c0> ``` Is there a special way to cache these eager loaded documents with Rails or Mongoid? FYI we're using Mongoid 4.