WhatsApp is ending support for a large number of older handsets.
The instant messaging service - which is owned by Facebook - has confirmed plans to discontinue support for a range of outdated smartphone models over the next year.
As revealed in a blog post, from December 31 WhatsApp will no longer support devices running the Windows Phone operating system.
From February 1 next year, the app will also stop working on phones on iOS 7 or older, as well as Android 2.3.7 and older.
While these phones are already technologically speaking in the past - the most recent Windows Phone handset was in 2015 - it could still be an issue for customers content with using their handset purely for messaging and calling.
In the blog post - which gets updated whenever new devices are added to the defunct list - WhatsApp explained: "While these mobile devices have been an important part of our story, they don't offer the kind of capabilities we need to expand our app's features in the future.
"This was a tough decision for us to make, but the right one in order to give people better ways to keep in touch with friends, family, and loved ones using WhatsApp.
"If you use one of these affected mobile devices, we recommend upgrading to a newer Android, iPhone, or Windows Phone before the end of 2016 to continue using WhatsApp."