An 18-year-old McDonald’s employee says he was fired from his job for calling attention to a serious health issue.

The teenager, identified only as Nick in a Buzzfeed News report, worked at a McDonald’s restaurant in LaPlace, Louisiana.

While refilling the ice cream machine, Nick spilled some of the mix. He attempted to clean up the mess, and in the process, he pulled out the machine’s inside trays.

“I was completely shocked by what I saw,” Nick told Buzzfeed News. “I thought it would be cleaned regularly.”

The inner tray seemed to be growing mold. Nick snapped a picture and informed a manager. He claims that nothing changed.

“The working conditions were ridiculous,” he said. “Everyone was inappropriate and nothing was clean.”

Nick shared the photos on Twitter, where they went viral, racking up more than 16,000 retweets.

That action cost him his job, as McDonald’s has a company-wide policy against publicizing anything that might “undermine the goodwill, reputation, development and/or operation.”

Buzzfeed News reached out to the restaurant, which noted a “long history passing regular health department inspections.” A McDonald’s spokesperson also said that the trays in question undergo regular cleaning, but never actually come into contact with the food.

Nick says that he’d always planned to post the pictures, but while he says that he was horrified at the conditions of his employer’s restaurant, he doesn’t believe that all McDonald’s operate the same way.

More than 80 percent of McDonald’s restaurants are owned and operated by franchisees, who maintain control over their facilities’ processes. The company requires franchisees to go through an extensive training process, which includes health and safety training.

So, did Nick really find mold in the ice cream machine?

Possibly. Ice cream machines are especially prone to fungal and bacterial growth. Food workers need to follow strict precautions to prevent contamination, particularly when refilling the machines.

Soda taps and ice machines can also attract mold, as the damp conditions are perfect for certain species of fungi.

In most parts of the country, health inspection codes only require the machines to be cleaned “at a frequency specified by the manufacturer” or “at a frequency necessary to preclude accumulation of soil or mold,” according to Food Safety Magazine. That means that some machines are only cleaned a few times per year, although some restaurants are much more diligent.

This isn’t much of a secret in the world of fast food. In one Reddit thread, McDonald’s employees discussed the prevalence of mold in their restaurants—especially around the soda taps.

“Yeah, I worked at a sub place that made us clean them every night, but I know those things mold up really fast if you don’t stay on top of them,” wrote Reddit user foxdye22. “Same with the ice machines. If I’m in a McDonald’s in general, I get my awful burger and get out.”

We’re still going to eat at McDonald’s—but we might skip the soft serve for a while.