Apple is having a bit of trouble with its latest marquee iPhone. The company said late Tuesday that the batteries in some of its iPhone 5s handsets are draining more quickly than they should.

“We recently discovered a manufacturing issue affecting a very limited number of iPhone 5s devices that could cause the battery to take longer to charge or result in reduced battery life,” Apple spokeswoman Teresa Brewer told AllThingsD. “We are reaching out to customers with affected phones and will provide them with a replacement phone.”

Apple declined to elaborate beyond that statement and wouldn’t say which 5s models have been affected and how widespread the problem is. But presumably “a very limited number” means just that. That the company has chosen to reach out to affected customers directly, rather than pointing them to a Web page to submit a replacement request suggests the number of iPhones with the issue is relatively small.

News of the battery issue and Apple’s response to it was first reported by the New York Times.