Batch processing #find_each and #find_in_batches causes object references to break

While trying to implement batch processing to alleviate memory bloat from a monolithic copy routine I discovered that I am unable to reference an ActiveRecord object via a belongs_to relationship even though the object id is set. Here is a basic example of what I'm talking about (within the context of batch processing):

my_comment = my_post.comments.create(:body => 'hello world')

my_comment.post_id 
=> 1

my_comment.post
=> nil

my_comment.reload
my_comment.post
=> nil

I've attached a patch that adds a test for the issue, but I can't for the life of me figure out why it is happening. If the batch processing is removed (call #each instead of #find_each) then the problem goes away.