Microsoft kicked off the rollout of a critical Windows Phone 8.1 update for its Lumia smartphones last week. The update is meant to fix some random reboots that Lumia owners experience in certain circumstances.

We reported last week that the update was making its way to Lumia 930 devices. Also, less than a week ago Microsoft rolled out the same critical update to Lumia 730, Lumia 830 and Lumia 1520 smartphones in India.

Today, the folks over at WindowsCentral report the same update is now available at AT&T for the following smartphones: Lumia 830, Lumia 1020 and Lumia 1520.

According to Microsoft, the reason for which they are now deploying this update is an issue they have found in some versions of Windows Phone 8.1 that would cause a Lumia smartphone to reboot periodically.

“We identified a problem in some versions of Windows Phone 8.1 that could cause a phone to restart periodically. A critical update will fix this problem. If you're unable to install the update or want to learn more, we can help you fix your phone.”

The update seems to be rolled out globally

Since Microsoft strongly recommends users to download and install this update, if you own one of the affected smartphones, you should check for its availability.

After applying it, your phone's OS version will be upgraded to 8.10.14234.375, while the firmware version will be bumped to 02040.00021.15063.02004.

On a side note, these are not the only Lumia smartphones receiving the update, as the Lumia 535 in Sweden, as well as Lumia 620 and Lumia 630 in India have been getting it as well.

This means that the critical update should be delivered to all affected Lumia smartphones in the coming weeks, so if you haven't received it yet, expect it to arrive pretty soon.