New York CNN Business —  

Investors are squarely concerned about the departure of Square’s chief financial officer.

The financial tech company’s stock has tumbled nearly 15% following the announcement on Wednesday that CFO Sarah Friar is leaving to become the CEO of Nextdoor.

Square CEO Jack Dorsey, who also runs Twitter, told employees he was “saddened” by the news. He acknowledged that it is Friar’s “lifelong ambition to run her own company.”

He added: “Sarah leaves us having established a culture of entrepreneurship and discipline across the entire company. She has been an amazing leader, partner, and friend, and we are grateful for all she’s done for Square.”

Dorsey also refuted a message on Twitter calling her departure “big” because she’s the “execution” of Square’s huge growth. The payment company offers digital readers and lets people with mobile phones and tablets accept card payments.

“We’re organized by business unit, like Cash, Caviar, Seller, Capital…and a lead/CEO for each,” he replied. “They are the execution, not me or Sarah. Square is built to be a durable ecosystem.”

Friar, who’s been with Square since 2012, is joining Nextdoor in December. The website describes itself as a “leading private social network for neighborhoods.”

Thursday’s loss comes amid a broader sell-off of tech stocks negatively impacting the markets. Still, Square’s stock is up a whopping 113% for the year.