During the winter, parents bundle their kids in heavy winter coats to keep them warm, but those same coats can pose an unexpected danger when the child is buckled in a car seat. Consumer Reports’ Child Passenger Safety Experts say that the extra bulk of a winter coat can make the safety seat harness too loose to properly secure your child in the event of a crash.

All that space that air takes up in puffy coat can compress in a car crash, meaning the car seat straps are actually too loose. Any slack or extra room in the straps means that there’s space for the child to be able to ride up, and be outside the protection of the car seat shell, which means he could have a head injury.”

Check if your child’s coat is too puffy by first securing her into the car seat wearing their coats so there is no slack in the harness straps. Then remove the coat and put him back in the seat and see if the straps are loose.

Instead of wearing a coat in their seat, Consumer Reports recommends securing your child into the seat and then putting a blanket or coat on top of the harness. For older kids put their coat sleeves on backwards after they are harnessed in.

Along with these tips, Consumer Reports suggests you periodically go to a car-seat checkup event to make sure your child’s seat is properly installed.