The Android 4.3 Jelly Bean update is rolling out to the Xperia Z1 and Zperia Z Ultra phones.
Sony announced that the roll-out has begun; it had already begun for the the Samsung Galaxy S3. The update is supposed to fix glitches such as phones freezing, or shutting down altogether.
Sony said in a blog post that the update brings better performance and smoother graphics.
Timing for updates for users of Xperia Z1 and Zperia Z Ultra phones will depend on markets and carriers, Sony said.