Apple is warning its store personnel that supplies of some replacement iPhones are running short, and extra measures may be required to assist customers.

According to an internal memo that AppleInsider has confirmed, Genius Bar personnel (Geniuses) have been informed that some iPhone replacements may be in short supply over the next few weeks. Geniuses are being encouraged “to offer to mail replacement devices to customers and provide ‘loaner’ iPhones in the meantime.”

Apple has already informed investors it will miss its quarterly guidance as its production and supply chain have been impacted as a result of measures to stop the spread of the coronavirus. Apple’s main manufacturing partner, Foxconn, just informed its own investors that it won’t be back to full production until the end of March, after weeks of its China factories being shut down or running at limited capacity.

Under Tim Cook, Apple is legendary for maintaining an extremely streamlined supply chain. This is one of the factors behind the company’s success clearing out old inventory right as new products are launched. In situations like these, however, a very tight supply chain can be a two-edged sword.

This latest warning by the iPhone maker is further evidence of the widespread impact the coronavirus is having.