Mercedes Benz is recalling some 54 units of its 2009 S-Class sedans because of an error in the door lock installation.

According to the notice filed with the National Highway Traffic Safety Administration, the locks of the front and rear passenger side doors could have been mismatched because of a labeling error.

The result? The passenger side door might not be opened by pulling on the interior handle and the rear door might be easily opened by pulling on the interior door handle even if it’s locked. The said condition can possibly prevent passengers from getting out fast when the need arises. It can also be dangerous to children sitting at the rear, who might unintentionally and accidentally open the door while the vehicle is running.

To correct the problem, Mercedes Benz will inspect vehicles and find the affected ones. The locks would be replaced for free.