Apple has acknowledged a flaw in certain Apple Watch models that could lead to the screen cracking, and has launched a replacement program for affected users. Apple or authorized service providers will replace the screen on eligible models free of charge.

“Apple has determined that, under very rare circumstances, a crack may form along the rounded edge of the screen in aluminum models of an Apple Watch Series 2 or Series 3,” the company says on its website. “The crack may begin on one side and then may continue around the screen as shown in the images below.”

The program only applies to aluminum Series 2 and 3 watches, including the Nike+ models and cellular variants. The original “Series 0,” the Series 1, and current Series 4 are not covered, and in the case of the Series 3, only models purchased through September 2019 are eligible. That could either mean Apple has fixed the problem in manufacturing or plans to discontinue the Series 3 this month — perhaps at next week’s iPhone event.

Stories of similarly cracked Apple Watch screens aren’t hard to find on social media, though it’s always hard to tell how widespread such issues are. A class action lawsuit in California was thrown out earlier this year for not sufficiently demonstrating the defective design.