Helpers in world not available from custom_env.rb

gistfile1.txt

features/support/helpers/admin_helper.rb:

  module AdminHelper
    def create_admin_user(whatever)
      # ...
    end
  end
  World(AdminHelper)

features/support/custom_env.rb:

  # I want to create some seed data shared by all scenarios
  create_admin_user('admin')

###

$ cucumber features/whatever.feature

  undefined method `create_admin_user' for #<Object:0x1763288> (NoMethodError)