Apple has quietly tightened its App Store rules to better protect users from developers who want to harvest their data or sell it to third parties. Previously, developers would ask for users’ phone contacts and sometimes then sold that data without the explicit consent of the users or their contacts, according to Bloomberg, which spotted the change.

The changes to the rules, which were made last week, explicitly state that developers are banned from turning address books into a database of contacts and from selling that database. They also can’t turn data into user profiles. Developers can still ask users for contact lists for use within their app, but they’ll have to tell users exactly what they’re going to do with the data. If they have more than one purpose in mind, they’ll have to ask for further consent.