Dapper one to many losing Id in the many - dapper

Question

Given the following two entities
public class Customer
{
public Customer()
{
Orders = new List<Orders>();
}
public int CustomerId { get; set; }
public string CustomerName { get; set; }
public List<Orders> Orders { get; set; }
}
and
public class Orders
{
public int OrderId { get; set; }
public int CustomerId { get; set; }
public int Quantity { get; set; }
public string OrderDescription { get; set; }
}
And the following code
string sql = #"
select c.CustomerId, c.CustomerName, o.OrderId as OrderId, o.CustomerId, o.Quantity, o.OrderDescription
from Customer c
join Orders o on c.CustomerId = o.CustomerId";
var customers = new List<Customer>();
Customer currentCustomer = null;
var c = connection.Query<Customer, Orders, Customer>(
sql, (customer, order) => {
if (currentCustomer == null || currentCustomer.CustomerId != customer.CustomerId)
{
customers.Add(customer);
currentCustomer = customer;
}
currentCustomer.Orders.Add(order);
return currentCustomer;
}, splitOn: "CustomerId, OrderId");
When I inspect customers the OrderId is always 0. As in customers.Orders[0].OrderId is zero, for all of them. Now I suppose it is me doing something wrong, but I can't figure out what. The strange SQL you see above is my attempts to try and force the OrderId to work.