On the heels of finally acknowledging “touch disease,” Apple is addressing a different problem with its iPhones – and is offering a free fix.

Apple said Sunday that it will replace the batteries of iPhone 6s models that are unexpectedly shutting down.

“This is not a safety issue and only affects devices within a limited serial number range that were manufactured between September and October 2015,” the company announced on its website.

Apple said owners of eligible phones can get their batteries replaced at the company’s stores or at authorized service providers, but not at wireless providers. The company also said that iPhone owners who have already paid for replacement batteries may be entitled to a refund.

Last week, the Cupertino company said it would repair iPhones that have “touch disease,” which causes flickering or unresponsive screens and is reportedly widespread. Apple said the problem – which it’s being sued over – likely stemmed from phones being dropped repeatedly. It said it would repair affected phones for $149.