BENTONVILLE, Ark. – Walmart made it official on Wednesday: Shoppers in Walmart and Sam’s Club outlets will be required to wear face coverings, effective July 20.

“While we’re certainly not the first business to require face coverings, we know this is a simple step everyone can take for their safety and the safety of others in our facilities,” Walmart U.S. chief operating officer Dacona Smith and Sam’s Club chief operating officer Lance De La Rosa wrote in a blog post. “According to the CDC, face coverings help decrease the spread of COVID-19 and because the virus can be spread by people who don’t have symptoms and don’t know they are infected, it’s critically important for everyone to wear a face covering in public and social distance.”

The executives noted that about 65% of the retailer’s 5,000 stores and clubs in the United States are located in areas where governments have mandated that shoppers were face coverings to help block the spread of COVID-19. Smith and De La Rosa said Walmart’s move will bring consistency across the chains.

“In addition to posting clear signage at the front of our stores, Walmart has created the role of Health Ambassador and will station them near the entrance to remind those without a mask of our new requirements,” the executives wrote. “Our ambassadors will receive special training to help make the process as smooth as possible for customers. The ambassadors, identifiable by their black polo shirt, will work with customers who show up at a store without a face covering to try and find a solution. We are currently considering different solutions for customers when this requirement takes effect on July 20.”

Walmart president and CEO Doug McMillon had discussed the possibility of a mask requirement for shoppers earlier this week in an online TV interview.

“It’s obviously something that’s on our minds,” McMillon said July 13 during an appearance on “Leadership Live with David Rubenstein,” a Bloomberg online TV show.

McMillon said masks are currently required in about 3,700 of its more than 5,000 U.S. locations “where either governor or someone else has mandated it.”

Despite the recent spike in COVID-19 cases in many states, few U.S. retailers have instituted mask requirements. In some instances, retail employees have been drawn into angry exchanges with customers who decline to wear masks.

The Retail Leaders Association (RILA) has asked governors to mandate that Americans wear masks when shopping. “Retailers are alarmed with the instances of hostility and violence front-line employees are experiencing by a vocal minority of customers who are under the misguided impression that wearing a mask is a violation of their civil liberties,” RILA president Brian Dodge wrote in a letter to the National Governors Association.

Masks do not prevent the wearer from contracting COVID-19 but minimizes the chance that the wearer will spread it to someone else.