How to use collection_check_boxes together with serialized Array

class Category < ActiveRecord::Base
  serialize :blocked_user_ids, Array
end

View:

<%= collection_check_boxes(:category, :blocked_user_ids, User.all, :id, :full_name) %>

The id of a blocked user is stored in the serialized attribute blocked_user_ids.

Passing checked/unchecked boxes for all users with collection_check_boxes to the controller works perfectly.

I wonder though how to show a checked box for each id that is stored in the blocked_user_ids array?