Disclosed is a follow-up fall prevention device used with a cord designed to secure a person. The device includes a blocking system having a pressure mechanism configured, during running of the cord, to be between the free weight and the bearing surface and to bias a free weight toward the cord and away from a bearing surface, thereby enabling the free weight to be always in contact with the cord and remain in the lower part of a cavity without touching the bearing surface, whatever the inclination of the cord and whatever the position of the device. The pressure mechanism includes a spring.