Rhino Mocks - Using Arg.Matches

I have a function I am mocking which takes an argument object as a parameter. I want to return a result based on the values in the object. I cannot compare the objects as Equals is not overriden.

I have the following code:

_tourDal.Stub(x => x.GetById(Arg<TourGet>.Matches(y => y.TourId == 2), null)).Return(
                new Tour() 
                {
                    TourId = 2,
                    DepartureLocation = new IataInfo() { IataId = 2 },
                    ArrivalLocation = new IataInfo() { IataId = 3 }
                });

This should return the object specified when the supplied parameter has a TourId of 2.

This looks like it should work, but when I run it, I get the following exception:

When using Arg, all arguments must be defined using Arg.Is, Arg.Text, Arg.List, Arg.Ref or Arg.Out. 2 arguments expected, 1 have been defined.

Any ideas what I need to do to resolve this?