no locking in xwiki?

I just edited a page with 2 users and last user won and was not notified that he was blowing away changes the other user just made. Is there a way to turn on locking in xwiki? I don't see this on the features list of xwiki but most wiki's have a feature to prevent a user from blowing away someone else's cahnges without knowing about it. procedure to reproduce: 1. login with user1 and click edit the home page 2. login with user2 and click edit the home page 3. have user1 make changes and save the page 4. have user2 make changes and save the page user1's changes are blown away and no one new about it. thanks, dean