If you have even a minor fear of heights, you may want to rethink a visit to Chicago’s Willis Tower.

In 2009, the building opened its revamped all-glass observation deck, known as Skydeck, to the delight of view-loving tourists everywhere. The glass enclosure allows people to get not only a panoramic view of the city but to also see the 1,353-foot drop below their feet. Cool right? Well, maybe not for everyone, as this week a few visitors got the scare of a lifetime when it appeared the glass flooring cracked below them.

Jesus Pintado, who was visiting the tower with his family, told NBC Chicago he was waiting in line when he heard a loud boom. According to Pintado, the people standing on the deck turned pale as they all heard the glass crack.

Though the incident seems like something out of a horror movie, everyone was safe the entire time.

“The protective coating which acts like a screen protector for the Ledge experienced some minor cracking,” a spokesperson for the Willis Tower told USA TODAY in a statement. “No one was ever in danger and the Ledge was immediately closed. We replaced the coating Monday night and the Ledge was open for business as usual yesterday.”

Willis Tower Skydeck, Chicago
Credit: Michael Weber/imageBROKER/Shutterstock

As the Skydeck’s website explains, the observation area is well-constructed and meant to withstand thousands of pounds of weight. It’s made out of iron, clear glass, which is “tempered for durability.” Each of the glass panels, it noted, weigh 1,500 pounds.

However, an eerily similar cracking incident took place in 2014, scaring visitors half to death then as well.

At the time, Alejandro Garibay told reporters he and his family experienced cracking when they stepped on the glass too.

“When we pulled our phones to start recording and take pictures they asked us to leave right away,” Garibay told NBC.

“Occasionally this happens, but that’s because we designed it this way,” a spokesperson for the building said following the 2014 incident. “Whatever happened last night is a result of the protective coating doing what it’s designed to.”

Still, maybe if hovering more than 1,000 feet in the air on glass they may potentially shatter under your feet isn’t your thing you sit this one out.