How to use ActiveModel's Validations & Callbacks on a custom class?

I am trying to use ActiveModel Validations & Callbacks on custom class.

class TestClass
  include ActiveModel::Validations
  define_model_callbacks :validate

  attr_accessor :test_field
  validates :test_field, presence: true # THIS IS CAUSING ISSUES!

  before_validate do 
    test_field.try('upcase!')
  end

  def custom_validate!
    run_callbacks :validate do
      puts "Done"
    end
  end
end

But I am receiving the following error:

Failure/Error:
  run_callbacks :validate do
    ...
  end
  NoMethodError: 
     undefined method `before_validate' for #<ActiveModel::Validations::PresenceValidator>

If I change callback name to something else than validate (e.g. validate_x) it works. Apparently validate is doing a bit more than I would expect. This error only happens if validates :test_field, presence: true is defined. For custom before_validate {} blocks it doesn't raise errors. Any idea how to fix this?