Mantain same VisitorId before and after user id is placed (no replies)

Hi,

We detected that value visitorId is different before and after user is identified by User Id. I'm explain. I browse to a site with piwik installed as anonymous user and piwik give me a visitorId. If another day I loged to this site and set User ID in nexts visits piwik give me another visitorId.

Is possible to not change visitorId after User ID is set? Whit this behavior we can know navigation path before User ID is set and after.

Thanks

Rubén