OtterBox has confirmed that a percentage of original OtterSpot wireless chargers may experience battery swelling. The company reassured customers that while some issues have been reported, there’s no danger in the swelling charging stations thanks to “internal safeguards” that prevent major malfunctions, meaning that devices presumably won’t explode or catch fire. The problem is only reportedly present in OtterSpots sold during a small window of 2019 when the stackable charging devices were first released.

Customers who purchased the original run of OtterSpots between July and August 2019 may notice the issue in their devices. The problem may be more prominent in chargers “under multi-stack and higher temperature conditions,” OtterBox said in a statement to The Verge. Despite the issue, OtterBox hasn’t recalled any devices, but the company is willing to replace OtterSpots that are experiencing the issue.

OtterBox has given a list of serial numbers for devices that could be defective, so even if an owner isn’t currently seeing any signs of battery swelling, it’s not a bad idea to check and see if a device is at risk. The company says that if an OtterSpot’s serial number starts with 229, 250, or 259, the device could be at risk. Those with defective charging stations can call the company’s customer service phone number (1-855-688-7269) and request a free replacement.

Luckily, it seems as if there won’t be too many affected devices as OtterBox confirmed that the OtterSpot was sold at limited retailers when it first launched. This means that the largest OtterBox retailers such as the Apple Store, Best Buy, and Target wouldn’t have sold any of the defective chargers, giving some peace of mind to many owners who purchased their devices through major outlets. It’s still not a bad idea to double-check the serial number to make sure that older charging stations won’t be affected, even if it was purchased through big retailers.