Fitbit has announced that chief financial officer (CFO) Bill Zerella is leaving the company after four years at the helm.

Replacing Zerella is Ronald W. Kisling, who has served as the company’s senior vice president and chief accounting officer since September 2014. Kisling held the CFO title at a number of other companies before starting at Fitbit.

Zerella joined Fitbit a year before it went public on the New York Stock Exchange (NYSE), having served as CFO at various firms over the previous two decades. However, Fitbit’s shares have essentially been in free fall since the company’s market debut in 2015. From its $20 IPO price, Fitbit surged to a high of more than $40 before sinking to less than $6, where it has remained over the past year.

Fitbit marginally beat Wall Street revenue expectations in Q1 2018, but its sales were down year-on-year as the broader fitness tracking market declined, with smartwatches on the up. Against that backdrop, Fitbit recently announced its second smartwatch and first wearable for kids, as it strives to capitalize on its brand in broader verticals. Earlier this week, Fitbit announced that it had shipped more than a million Versa smartwatches since they went on sale in mid-April, making the Versa one of its biggest products to date.

In terms of where Zerella is heading now, well, according to Fitbit he’s going to flex his CFO chops at an autonomous vehicle startup, though the name of the company wasn’t revealed. Zerella’s last day at Fitbit will be June 15, 2018.

“Over the past four years, Bill’s passion and dedication to growing early-stage companies were key enablers of Fitbit’s transformation from a startup to the leading global brand it is today,” said Fitbit cofounder and CEO James Park. “We thank him for his countless contributions, including leading our successful IPO in 2015, guiding our worldwide expansion, and laying the foundation for our future success.”