Why Castle ActiveRecord's OnUpdate is called twice?

Question

Hi all,

I have override OnUpdate and do some logging with it. But unfortunately it is called twice. Why such thing happens? How it could be corrected?

Thanks in Advance

UPDATE:

I have extended ActiveRecordBase as follow:

public class ActiveRecordExtender<T> : ActiveRecordBase<T>
{
    protected override void OnSave()
    {
        DoSomeOperation();
        base.OnSave();
    }

    protected override void OnUpdate()
    {
        DoSomeOperation();  
        base.OnUpdate();
    }
 }