Mongoid for some reason does not pick up the reverse many-to-many self-association of the model?

Question

ruby

The model looks like this in a nutshell:

class Task
  include Mongoid::Document
  has_and_belongs_to_many :dependent_tasks, class_name: "Task", inverse_of: :depending_tasks
  has_and_belongs_to_many :depending_tasks, class_name: "Task", inverse_of: :dependent_tasks
  attr_accessible :dependent_tasks, :depending_tasks
end

But for some reason it looks like this:

task.depending_tasks << task2 #=> [#<Task _id: 52fa6127e826a69ea2000002, parent_id: nil, dependent_task_ids: ["52fa6123e826a69ea2000001"], depending_task_ids: nil>]

task2 #=> #<Task _id: 52fa6127e826a69ea2000002, parent_id: nil, dependent_task_ids: ["52fa6123e826a69ea2000001"], depending_task_ids: nil>

task2.dependent_tasks #=> []
task2.dependent_task_ids #=> ["52fa6123e826a69ea2000001"]

Judging by the fact that dependent_task_ids exists, it looks like the problem is in mongoid.
How can it be corrected?