Billionaire entrepreneur Elon Musk, who has been teasing an upgrade to Tesla’s Autopilot software for weeks, said on Wednesday morning that version eight of the software “starts downloading tonight.”

Musk, who made the comments on Twitter, added that the release of the software to customers will be gradual to avoid issues, and the upgrade will be “a major overhaul on almost every level.”

Tesla’s TSLA Autopilot software launched last October and uses sensors—like radar and a camera—combined with computing and software to take over various parts of driving like lane changing and steering. It’s available on many of Tesla’s new Model S and Model X cars.

But earlier this summer, Tesla revealed that a customer had been killed while using Autopilot. Regulators decided to investigate the accident and Tesla’s Autopilot system.

Other Tesla customers have complained that Autopilot hasn’t worked correctly and has caused accidents, though Tesla has denied most of those claims. Recently, a Chinese man filed a lawsuit against Tesla, alleging that Autopilot malfunctioned in his son’s car and caused a serious crash that killed his son.

Musk has said that the latest upgrade to Autopilot will process radar signals better, meaning it will likely be able to better detect some objects that could be harder to see because of light, color, or weather. In the fatal accident with Autopilot, the driver collided with a tractor-trailer when the software didn’t detect it partly because of the white color of the tractor-trailer against the bright sky.

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Musk said recently that the new features on Autopilot could have prevented the death of the U.S. Tesla customer, though Autopilot 8.0 won’t deliver perfect safety.

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Musk has been tweeting about the upgrade for several weeks. Last week, he tweeted that the next upgrade would happen today.