.net - Enverse store information as nulls for not update properties

Question

I am developing an mvc application and I am using fluent nhibernate and enverse to store information in db and to auditing my data.

My base class for entities looks like:

[Audited]
public class EntityBase : IEntity
{
    public virtual int ID { get; set; }
    public virtual string CreatedBy { get; set; }
    public virtual string ModifiedBy { get; set; }
    public virtual DateTime CreatedDate { get; set; }
    public virtual DateTime? ModifiedDate { get; set; }
    public virtual bool IsActive { get; set; }
}

My fluent mapping:

internal class EntityMap<T> : ClassMap<T> where T:EntityBase
{
    public EntityMap(string tableName = null)
    {
        Id(x => x.ID).DefaultStrategy<T>(tableName);

        if (!string.IsNullOrEmpty(tableName))
            base.Table(tableName);

        Map(x => x.IsActive).Not.Nullable();
        Map(x => x.CreatedDate).Not.Nullable().Not.Update().CustomType("Timestamp");
        Map(x => x.CreatedBy).Not.Update();
        Map(x => x.ModifiedDate).CustomType("Timestamp");
        Map(x => x.ModifiedBy);
    }
}

When I store each entity to db then action on pre insert is running and it sets values for createdDate and createdBy.

I have a problem when i am updating an entity. CreatedDate and CreatedBY are not update fields so I don't store this information in my viewmodel so during conversion to model/entity a have no information about createdDate and createdBy. In my table I have all information after edit and entitybase but in auditing I receive a new row with empty CratedDate and CreatedBy.

is there any way to configure enverse to not lose this data?