How to inherit from other class in different level

Hi, I've a problem since I need a Class to inherit from other Class
that is in other level. The problem is this:

···

---------------
module SIP
  class SipUri
    class SipUriParameters
    end
  end
end

module SIP
  class TelUri
    class TelUriParameters < SipUriParameters
    end
  end
end
-----------------

NameError: uninitialized constant SIP::TelUri::SipUriParameters
        from (irb):9

Well, I can solve it by using:

  class TelUriParameters < SIP::SipUri::SipUriParameters

but is not other way? Thanks a lot.

--
Iñaki Baz Castillo
<ibc@aliax.net>