Burger lovers will have to get used to eating off fast-food trays inside McDonald’s again.

McDonald’s Corp. is facing tight supplies of some of its paper to-go bags, the latest supply challenge affecting U.S. restaurants. The chain recently told restaurant owners that they needed to limit orders of bags from suppliers as usage is running ahead of already high numbers last year, McDonald’s said in an internal message.

Many customers are asking for their Big Macs, McNuggets and fries in bags even when they dine inside, driving the tightness, the chain said in the message. Workers who have spent months packing all orders to go during the pandemic aren’t used to serving meals on trays, contributing to the strain, the company said.

“Many new crew members have never had to deal with trays before,” the company said in the late-July message. The “transition to using trays has been slower, more difficult because we haven’t done it in so long.”

McDonald’s said that while bag supplies have been pressured for the chain and others in the industry, impact to its restaurants was minimal. “We are confident customers should not see disruption,” the company said. “We will continue to watch closely.”