Automapper ProjectTo nested object

I'm trying to use the Queryable-Extensions ProjectTo method with Entity framework inside my WebApi. It works good for normal objects but when I try to use nested objects, Linq cannot translate the Map method for the nested object into a store expression.

var entity = db.tableX.where(x => x.ID == id).ProjectTo<MyDtoObject>().FirstOrDefault();

Automapping config:

CreateMap<EntityModel.tableX, MyDtoObject>()
     .ForMember(dest => dest.Id, opts => opts.MapFrom(src => src.id))
     .ForMember(dest => dest.TestObject, opts => opts.MapFrom(src => Mapper.Map<TestObject>(src)))


CreateMap<EntityModel.tableX, TestObject>()
            .ForMember(dest => dest.Id, opts => opts.MapFrom(src => src.ForeignKey1.Id));

How can I use this ProjectTo() method with a nested object? I know other solutions with a normal Select statement, or mapping from a query into memory list, will also work..