Terex South Dakota is recalling certain 2013-2015 model-year aerial device and digger derrick trucks because the vertical cylinders and outriggers might drift when loaded and cause the platform to fall, the National Highway Traffic Safety Administration reported.

Outrigger drifting poses an injury risk to both occupants and bystanders, NHTSA said. The recall covers trucks manufactured from June 3, 2013, through November 13, 2014. But at the time of the recall notice filing, Terex South Dakota hadn’t yet determined how many trucks were involved.

To fix the problem, dealers will install the orifice and replace the affected valves, free of charge. Truck owners can reach Terex customer service at (605) 882-4000. Terex’s number for this recall is SN619.