Sen. Dick Durbin did what few could do at Tuesday’s combined Senate Judiciary and Commerce committee hearing investigating Facebook’s abuse of its users’ private data. He cracked Mark Zuckerberg’s otherwise stiff facade.

“Mr. Zuckerberg, would you be comfortable sharing with us the name of the hotel you stayed in last night?” Durbin asked.

A look of mild panic crossed the CEO’s face. (He probably hadn’t thought to prepare a scripted answer to that particular question before the hearing). After an awkward five-second pause, full of “ums” and nervous laughter, Zuckerberg responded with a firm “no” and a sheepish smile as the crowd burst into laughter.

The Democratic senator from Illinois continued: “If you’ve messaged anyone this week, would you share with us the names of the people you’ve messaged?” To which Zuckerberg—committed now—promptly responded, “Senator, no, I would probably not choose to do that publicly here.”

Durbin’s questions got to the heart of the issues confronting Facebook in the wake of the Cambridge Analytica scandal. Users have a right to privacy, and they have a right to limit what personal data Facebook collects and shares with other parties. As the exchange showed, Zuckerberg clearly values his own privacy, but he is seemingly less concerned with that of Facebook’s users.

Read more from Slate on Cambridge Analytica.