I am mapping source object

public class PlannedCare
{
    public int OrderNumber { get; set; }
    public PlannedCareBatch? BatchStart { get; set; }
}

to

public class PlannedCareDto
{
    public int OrderNumber { get; set; }
    public PlannedCareBatchRm? BatchStart { get; set; }
}

Config:

var config = new MapperConfiguration(cfg => {
    cfg.AllowNullDestinationValues = true; //this is default, but just to make sure...
    cfg.CreateMap<PlannedCare, PlannedCareRm>();
    cfg.CreateMap<PlannedCareBatch, PlannedCareBatchRm>();
    // other mappings...
});

All is OK if I use Map method. When I use ProjectTo the destination BatchStart object is always initialized. I want it to remain null if source property BatchStart is null. I am using Mongo DB driver. Where is the problem?

public IQueryable<PlannedCareDto> GetQueryable()
{
    return _collection
        .AsQueryable()
        .ProjectTo<PlannedCareDto>(_mapper.ConfigurationProvider);
}

I even tried setting NullSubstitue on property, which also does not work. I guess the query will be somehow malformed…

CreateMap<PlannedCare, PlannedCareRm>()
    .ForMember(p => p.BatchStart, d => d.NullSubstitute(null));