Portable chargers and power banks might be useful additions to your carry-on luggage, but they’re also a potential fire risk. Now Southwest Airlines is tightening rules around their use on board aircraft.

Citing safety concerns, Southwest Airlines will no longer allow passengers to charge devices with a power bank stowed inside a carry-on bag—going further than current FAA guidance.

Southwest Airlines is implementing new restrictions surrounding portable batteries in the interest of passenger safety. The airliner is now prohibiting the use of portable batteries to charge devices while inside bags because they can pose a fire risk, Southwest Airlines tells PEOPLE.