The fast-casual purveyor on Thursday announced that Chief Financial Officer Jeff Uttz—who has served in that role since September 2013 and helped Shake Shack go public in early 2015—will retire this year. No word on who will replace him in that role, though Uttz will remain as CFO through mid-March to oversee the company’s fiscal 2016 results. He is also set to speak at the ICR Conference in Orlando, Fla., next week along with CEO Randy Garutti. A search for a successor is underway.

Meanwhile, Shake Shack (SHAK) also named Zach Koff to the company’s first chief operating officer post. Koff is an internal hire, as he has been leading operations at Shake Shack since it opened the company’s fourth restaurant. He has been a member of the company’s executive team since the initial public offering.

“I am beyond proud of Zach’s leadership over the last six years,” said Garutti. “He has built the team and systems that run our restaurants today and has been at the foundation of Shake Shack’s unique and powerful people culture.” Garutti added that while the company hasn’t closed the books on the fourth quarter yet, the company remains “confident” in the 2016 financial guidance targets it disclosed in November.

Koff and the new CFO will play critical roles in helping Shake Shack maintain a solid pace of sales growth that has far exceeded the industry’s average—though persistent concerns about the strength of those sales increases have put pressure on the stock since a strong start at the time of the IPO.

In the operations role, Koff will be keenly focused on making sure new Shacks get up and running as smoothly as existing locations. The company opened its 100th global location this past fall and expects to open around 20 new locations in the U.S. alone for 2015. It sees potential for 450 restaurants domestically in the long term.