One of the glass enclosures known as The Ledge that sticks out of Willis Tower cracked under the feet of a California family, according to a report.

NBC5 reports that the Alejandro Garibay family heard it cracking after they stepped out on the enlcosure about 9:50 p.m. Wednesday. They stepped off and alerted staffers.

Willis Towers officials have not responded to a request for comment.