Starting July 1, the retailer (and its corporate cousin Sam’s Club) will institute the new policy as well as discontinue the sale of fruit- and desert-flavored nicotine products. The company made the announcement in a letter to the Food and Drug Administration Wednesday.

Walmart is also instituting more severe penalties for cashiers who don’t follow the policies, saying employees who fail secret shopper checks “will be subject to disciplinary action, up to and including termination.”

“We unequivocally acknowledge that even a single sale of a tobacco product to a minor is one too many, and we take seriously our responsibilities in this regard,” said John Scudder, Walmart’s ethics and compliance officer.

The move comes amid increased Congressional pressure to force retailers to raise the legal age to buy tobacco products from 18 to 21.

Earlier this month, Senate Majority Leader Mitch McConnell announced plans to introduce a bill that would do just that. Several states have already enacted such laws.

Government health officials have been increasingly worried about teen smoking, noting that teens who vape are more likely to start smoking cigarettes. Tobacco smoking adults that use vapes also have a significantly higher chance of heart attack, coronary heart disease and depression, according to the largest-ever study conducted on vaping, published in March.