Object-Data getting lost

When iterating with a cursor over a set of Mongoid Documents, the changes to those objects are lost outside the loop. Is this the expected behaviour?

Please have a look at 'spec/computer_spec.rb'

Run the spec with: rake

What?

class Computer
  include Mongoid::Document
  field :active, type: Boolean
  field :dirty, type: Boolean
end

This fails:

 computers = Computer.all
 # computers = Computer.all.to_a fixes the problem

 computers.each do |c|
   c.active = true
   c.dirty = false
 end

 computers.each do |c|
   c.save
 end

 # nothing gets updated