流畅验证 - 内部集合未验证

有类似于FluentValidation集合属性未验证的问题，不幸的是他们的修复不起作用。任何想法为什么底层订单验证器不参与？

validator.Validate(client, ruleSet: "Production");
public class ClientValidator : AbstractValidator<Client>
{
    public ClientValidator()
    {
        RuleSet("Production", () =>
        {
            RuleFor(client => client.Orders)
                .NotEmpty();
            RuleFor(client => client.Orders)
                .SetCollectionValidator(new OrderValidator());
        });
    }
}
public class OrderValidator : AbstractValidator<Order>
{
    public OrderValidator()
    {
        RuleSet("Production", () =>
        {
            RuleFor(x => x.Items)
                .NotNull();
        });
    }
}