Costco has 14 Colorado locations, and they are getting stricter about enforcing their membership rules after seeing more non-members using membership cards that don’t belong to them at self-checkouts.

The store’s policy requires shoppers to have a paid membership to shop there, and they must show their membership cards when entering the warehouse and scan them when checking out. However, there really hasn’t been anything in place to prevent someone from using a membership card that wasn’t theirs… Until now!

To crack down on unauthorized card-sharing, Costco said employees are now asking to see shoppers’ membership cards with their photo at self-checkout. If the membership card does not have a photo, then employees ask for a photo ID.

“Costco is able to keep our prices as low as possible because our membership fees help offset our operational expenses, making our membership fee and structure important to us,” Costco said in a statement. “We don’t feel it’s right that non members receive the same benefits and pricing as our members.”

Costco’s basic Gold Star membership costs $60 per year and Executive memberships cost $120 annually and come with extra perks. Both tiers allow for two individual cards per membership.