A row unit of a header for an agricultural harvester having a gathering chain lockout assembly is provided. The row unit includes a frame, a gathering chain assembly and a lockout assembly that allows adjustment or removal of the gathering chain. The gathering chain assembly is mounted to the frame extending forwardly of the header and includes first and second sprockets, an endless chain extending between the first and second sprockets, and a carriage assembly extending from and supporting the first sprocket. The carriage assembly has a stationary member and a moveable member moveable relative to the stationary member between an extended position and a retracted position. The lockout assembly is attached to the carriage assembly and includes a lockout fastener pivotably attached to one of the stationary member and moveable member and an engaging member attached to the other of the stationary member and moveable member.
