protobuf-net and an empty property in subclass
===

I was trying to use protobuf-net and faced with the following problem.
I have two classes.
<!-- language-all: c# -->

    [ProtoContract]
    class parent
    {
        [ProtoMember(1)]
        public string name { get; set; }
    }

    [ProtoContract]
    class child : parent
    {
        [ProtoMember(2)]
        public int num { get; set; }
    }

If I create a child object without setting the child property "num"

    var obj = new child() { name = "tester" };

and try to serialize it

    using (var stream = new MemoryStream())
    {
        Serializer.NonGeneric.Serialize(stream, obj);
    }

the stream will be empty.

Is there any way to handle this situation without using the attribute [ProtoInclude] for the parent class?<br>
I'm using protobuf-net v2 r480.

Thanks