Automapper IValueResolver does not support Nullable type Guid

Question

Recently I updated automapper 5+ version and realized that IValueresolver does not work as expected for Nullable type Guid.

I have created a value resolver as follows:

public class GanttTaskParentIdResolver : IValueResolver<GanttTask, Task, Guid?>
{
    private IUow Uow;
    public GanttTaskParentIdResolver(IUow _uow)
    {
        Uow = _uow;
    }
    public Guid? Resolve(GanttTask source, Task destination, Guid? member, ResolutionContext context)
    {
        if (source.parentIdRaw != null && source.parentIdRaw != 0)
        {
            var task = Uow.Tasks.GetAll().Where(con => con.Id == source.parentIdRaw).FirstOrDefault();
            return task.GUID;
        }
        else return null;
    }

}

and Mapping configuration as follows:

cfg.CreateMap<GanttTask, Task>()
              .IgnoreAllNonExisting()
              .ForMember(dst => dst.Children, opt => opt.MapFrom(s => s.Children))
              .ForMember(dst => dst.ParentId, opt => opt.ResolveUsing<GanttTaskParentIdResolver>())
              .ForMember(dst => dst.CalendarId, opt => opt.ResolveUsing<GanttTaskCalendarIdResolver>());

The dst.ParentId is Nullable Guid. It does not trigger GanttTaskParentIdResolver for resolving and always gives null for ParentId.

Anyone experienced the same issue?

Update - i tested for nullable int and it works. it seems a issue with nullable Guid