On Saturday, Tesla Motors CEO Elon Musk announced that a major new software update was being sent to a small number of newer Tesla vehicles, with more ideally updated over the coming week. The update, 8.1, will include upgrades to the cars’ Autopilot feature.
Get Data Sheet, Fortune’s technology newsletter.
This update is specific to vehicles with the enhanced hardware package that Tesla made standard starting in October. That hardware includes more cameras, ultrasonic sensors, radar, and a much more powerful onboard computer.
But those newer vehicles didn’t initially have some of the Autopilot features beloved by owners of existing Teslas, including automatic emergency braking and lane guidance. In October, Tesla said the new system needed more validation before those features would be activated.
According to Bloomberg, the new update will enable those missing features on newer cars. But sources speaking to Elektrek claim that some of those features will be limited, with Autosteer only working when vehicles move slowly on clearly-marked highways.
For more on TK watch our video.
That limitation is thanks to the hurdle of adapting the Autopilot functions to Tesla’s own imaging system, adopted after the carmaker split with Israel’s Mobileye. That rift was triggered at least in part by a fatal Tesla crash in May 2016, after which Tesla was seen by some as shifting blame to Mobileye’s cameras.
What the 8.1 update does not include is the full autonomy that the new generation of Teslas are built to be capable of. It’s still unclear when those capabilities might be rolled out to owners, but Musk has predicted that a Tesla would make an entirely autonomous coast-to-coast demonstration trip by the end of 2017.