Patch and related entities

Models

    public class TestA
    {
        public int Id { get; set; }
        public int Value { get; set; }
        public TestB B { get; set; }
    }

    public class TestB
    {
        public int Id { get; set; }
        public string Value { get; set; }
    }

When creating a TestA entity by doing:
POST {"@odata.type":"#Test.TestA","Value":4, "B@odata.bind":"http://localhost:52773/api/TestBs(1)"}
the controller receives a TestA-object with A.B instantiated and B.Id set to 1.

When updating a TestA entity by doing:
PATCH {"@odata.type":"#Test.TestA","Value":5, "B@odata.bind":"http://localhost:52773/api/TestBs(2)"}
the delta received in the controller doesn't contain the Id of B.