upload_url_path doesn't seem to make any effect

[avibrazil]

An site of mine had ​http://site.com/articlefiles/ as the place to receive uploads, equally it was /site/root/articlefiles on the filesystem, instead of /site/root/wp-content/uploads.

Now I migrated the site into a multisite installation as site 2 and uploads are going into /site/root/articlefiles/site/2/ and all previous uploads in old posts are linked as ​http://site.com/articlefiles/site/2/something.jpg, causing broken images and links cause they originally don't have the "site/2" part. Editing the post, these links and images do not have the "site/2" part either. WordPress is rewriting the URL dynamically when reading the posts.

I want to keep compatibility with ​http://site.com/articlefiles/ and /site/root/articlefiles without the "site/2" part. I was expecting upload_url_path on options table to be the solution but it doesn't work. I put there ​http://site.com/articlefiles/.

How can I keep URL and path compatibility when migrating a single site to a non-primary site of multi site installation ?

Thank you in advance