Macau casino operator stocks are taking a pounding on reports of plans to halve the amount that UnionPay bank card customers can withdraw from Macau’s automated teller machines.

On Thursday, the South China Morning Post reported that the Monetary Authority of Macau planned to reduce the UnionPay daily withdrawal limit from MOP 10k (US $1,250) to just MOP 5k. The new limit is set to take effect this Saturday (10).

UnionPay card abuse in Macau has been a problem for years but this new restriction was reportedly sparked by some particularly brazen tactics. The SCMP quoted a source saying “individuals are turning up at ATM machines with stacks of cards from individual account holders and withdrawing MOP 10k a time,” resulting in as much as MOP 10b ($1.25b) in withdrawals in just a single month.

UnionPay cards play a key role in helping mainland Chinese residents acquire gambling funds in Macau. A popular method involves using the card to purchase a luxury item at a Macau pawnshop, then selling the item back to the pawnbroker for cash, less a commission.