Namespaced rule keys translation?

I am trying to use namespace configured in contract to scope my rule keys translations. Documentation seems to be lacking in this regard.

module UserAuthentication
  class AuthenticateWithPassword < ApplicationContract
    config.messages.namespace = 'user_authentication/authenticate_with_password'
    ...
  end
end
ru:
  dry_validation:
    rules:
      password: пароль1 # works
      email: email1 # works
      user_authentication/authenticate_with_password: # doesn't work
        password: пароль2
        email: email2
    user_authentication/authenticate_with_password: # doesn't work
      rules:
        password: пароль3
        email: email3