Before you hand that sippy cup over to your toddler, you might want to take a minute to make sure it’s not one of a few million spill-proof vessels being recalled due to risk of mold. We may not know everything about kids here at Consumerist, but we’re willing to bet swallowing mold wouldn’t be a popular experience.

Mayborn USA is calling back 3.1 million Tommee Tippee Sippee cups because mold can develop on a removable, one-piece valve inside the cups, if the piece gets wet (which it will if you’re using it) and stays wet, and is “infrequently cleaned,” the Consumer Product Safety Commission says.

The cups have a 7 to 10 oz. capacity and were sold for children ages 4 to 12 months. They were sold in a bunch of places: BuyBuy Baby, CVS, Giant, Kohl’s, Marco Baby, Marshalls, Meijer, Sam’s Club, Ross Stores, Target, Bealls Outlet, Walgreens, Wal-Mart and other mass merchandise stores nationwide, as well as online at Amazon.com, Babyhaven.com, and Diapers.com from December 2014 through May 2016 for between $4 and $7.

“What’s a little mold?” you might be saying. Well, it might not make you feel very good, the CPSC says, noting that ingesting it can pose “a risk of gastrointestinal symptoms and infections in consumers with compromised immune systems.”

Consumers should immediately stop using the recalled Sippee cups and contact Mayborn to receive a free replacement cup.