Facebook will end support for its Messenger app on a number of smartphones this week.
The hugely popular messaging app will no longer work on smartphones running Windows 8.1 or earlier.
Facebook has reportedly started emailing users who are affected.
“Thank you for choosing to use Messenger,” Facebook says in its email.
“We regret to inform you that since the end of March, the app version you’re using is no longer supported and you can no send and receive messages.”
“To continue to send and receive messages from Facebook on your phone, update your Facebook app to the latest version,” the company added.
Facebook Messenger isn’t the only app to end support for Windows powered smartphones in recent months.
Earlier this month Microsoft announced it was ending support for Skype for users with older Windows devices.
WhatsApp has also confirmed it would end support for its app on Windows phones by 2017.
Windows Phone remains in decline and has just a 0.3 percent share of the market dominated by Android and iOS powered devices.
Last week Facebook announced its Stories feature would be coming to Messenger.
The new feature is very similar to SnapChat stories and allows users to post short video clips, GIFs and photographs.