Apple’s iPhone 12 has been a hit in sales and that means expectations are high for the upcoming announcement of its financial results this week. Here comes the buzzkill, Apple is now warning millions of iPhone 12 owners that its iPhone 12 devices and their MagSafe wireless chargers can possibly cause electromagnetic interference with medical devices such as pacemakers and defibrillators.

“Medical devices such as implanted pacemakers and defibrillators might contain sensors that respond to magnets and radios when in close contact. To avoid any potential interactions with these devices, keep your iPhone and MagSafe accessories a safe distance away from your device (more than 6 inches / 15 cm apart or more than 12 inches / 30 cm apart if wirelessly charging). But consult with your physician and your device manufacturer for specific guidelines.”

Apple mentioned that its official MagSafe Charger and MagSafe Duo Charger are accessories that can cause interference.

Apple’s warning comes after a report in the Heart Rhythm Journal earlier this month, which claimed iPhone 12 models can “potentially inhibit lifesaving therapy in a patient” due to magnetic interference with implantable medical devices.

Apple has shared that “though all iPhone 12 models contain more magnets than prior iPhone models, they’re not expected to pose a greater risk of magnetic interference to medical devices than prior iPhone models” but adds the caveat “If you suspect iPhone or any MagSafe accessories are interfering with your medical device, stop using your iPhone or MagSafe accessories.”