Tesla Chief Financial Officer Zach Kirkhorn has stepped down after more than four years in the role, where he worked behind the scenes to translate Elon Musk’s ambitions into reality.

The electric-car maker on Monday said Chief Accounting Officer Vaibhav Taneja had been appointed as CFO on Aug. 4, when the 38-year-old Kirkhorn left the position.

His surprise move comes ahead of Tesla’s Cybertruck pickup coming to market later this year and raises questions about succession planning for Musk, who is 52 years old and runs several companies, including SpaceX and X, the social-media platform formerly known as Twitter.

Tesla has no clear second-in-command, but board members had discussed Kirkhorn as a possible successor to Musk as CEO, The Wall Street Journal reported in May.

Shares were down around 2% in early-afternoon trading. Over the weekend, Musk said he may need to have more neck surgery.