How can C# nullable value typed values be set on NHibernate named IQuery parameters?

OK, it turns out there are some overrides on SetParameter that allow the type to be set explicitly. For example:

query.SetParameter(position, null, NHibernateUtil.Int32);

The full extension methods (for Int32 and DateTime only) are now:

public static class QueryExtensions
{
    public static void SetInt32(this IQuery query, int position, int? val)
    {
        if (val.HasValue)
        {
            query.SetInt32(position, val.Value);
        }
        else
        {
            query.SetParameter(position, null, NHibernateUtil.Int32);
        }
    }

    public static void SetInt32(this IQuery query, string name, int? val)
    {
        if (val.HasValue)
        {
            query.SetInt32(name, val.Value);
        }
        else
        {
            query.SetParameter(name, null, NHibernateUtil.Int32);
        }
    }

    public static void SetDateTime(this IQuery query, int position, DateTime? val)
    {
        if (val.HasValue)
        {
            query.SetDateTime(position, val.Value);
        }
        else
        {
            query.SetParameter(position, null, NHibernateUtil.DateTime);
        }
    }

    public static void SetDateTime(this IQuery query, string name, DateTime? val)
    {
        if (val.HasValue)
        {
            query.SetDateTime(name, val.Value);
        }
        else
        {
            query.SetParameter(name, null, NHibernateUtil.DateTime);
        }
    }
}