RSS feed only works for entire wikis, not for spaces and documents lists

Watchlist rss feed is empty even if a document has just been modified.

Tested both with a clean installation and a migrated one from version 1.5.
How to reproduce with a clean installation (installed with default data imported):
1. Login with Admin/admin
2. While on the "Welcome to your wiki" page, click 'watch this space' from 'watch' menu.
3. Do some modifications to the current page
4. Select "Manage your watchlist" on the "watch" menu.
5. From the watchlist manager, open the rss feed named "Last modifications feed for your watchlist"

It should have the current page, but it is empty.