Firmware updates are available for the three X-Mount primes, 18, 35 and 60mm lenses. This is a fairly minor update, but I would always recommend you are using the latest firmware.
The update improves focus accuracy when using the AF-L button to focus.
Get the update here. You can download all three lens firmware files and put them on the same SD card, so no need for messing about. To update hold the DISP button whilst turning the camera on and follow the on-screen instructions.