Popular cross-platform messaging service WhatsApp is shifting its iOS app from a flat-fee purchase to a $0.99 annual subscription model sometime this year, reports TechCrunch. The move would bring pricing in line with WhatsApp’s other offerings on Android, Windows Phone, and BlackBerry, and possibly making it free to use for the first year, as it is on those platforms.

WhatsApp CEO Jan Koum revealed the plan to a Dutch journalist Alexander Klöpping, saying that while the company is relaxed on exact dates, the switch is definitely on the 2013 road map. It’s important to note that the new pricing will only apply to new users — if you’ve already downloaded WhatsApp on iOS, you’ll escape the recurring charges. Koum didn’t explain his motivations for the switch, but we suspect it may have something to do with constantly being asked to defend the differentiated pricing. And for those holding out hope for a desktop app, we have some unfortunate news — the CEO says the service is staying mobile-only for the foreseeable future.