ServiceStack.Swift Error in generated code

The Swift generator does not generate valid Swift code for the following .Net code.
The error is 'Redundant conformance of ‘XXX’ to protocol ‘JsonSerializable’.

    public class Class1 : IReturn<SomeClass>
    {
    }
    public class Class2 : IReturn<SomeChildClass>
    {
        public SomeClass Classy { get; set; }
    }
    public class SomeClass
    {
        public string SomeValue { get; set; }
    }
    public class SomeChildClass : SomeClass
    {
        public string SomeChildValue { get; set; }
    }

Please read the Swifts limitations, Base classes need to be abstract.