On-demand car service Uber is saying goodbye to its Chief Financial Officer.

Brent Callinicos, who served as CFO of the startup since 2013, is stepping down to spend more time with his family.

“For me, this ride is coming to an end. After 26 years of nonstop work since MBA School, I am going to step back and spend some time with my family and let someone else take this amazing company to the next level as CFO. My daughter is in middle school; my wife has been supportively waiting to spend time with me for 28 years. I made a promise to both of them that I would be taking a long break at this stage of life. And as the great philosopher put it, everything has conspired to give me this opportunity to acknowledge my heart’s desire. Right now, the happiest thing I can think of is driving my daughter to school and swim practice. Time, now, for the heart’s desire,” he said in an email to Uber staff obtained by the Wall Street Journal.

Uber has not yet named a replacement, and Gautam Gupta, whom Uber CEO Travis Kalanick describes as “Brent’s right hand on Strategic Finance,” will be the acting head.

“Almost 2 years ago, I brought on one of the great financial operators in Silicon Valley as our CFO. Though two years sounds short, Uber was a much smaller startup then – about 1/10th the size we are today. Brent has provided critical leadership to take Uber to the next level as we matured as a company. We have financial systems in place overseeing operations in 53 countries. We have a deep bench of talent poised to help our finance organization grow with the business,” said Kalanick in a memo to investors.

Kalanick says Callinicos will serve the company as an “advisor”.

Under his watch, Uber has grown to a valuation of over $40 billion. Callinicos is stepping down just as an IPO seems imminent.