Density control system for an agricultural baler having a baling chamber including a plurality of walls with at least one movable wall section, an intake duct leading into the baling chamber, and a plunger for compressing charges of crop material to a package in the chamber, an actuator for adjusting the position of the at least one movable wall section in response to an output of the density control system to vary the density of said package, wherein the density control system has a sensor for measuring the position of the at least one movable wall section, a comparator for comparing said position with a threshold position and a decision module configured to stop the movement of the actuator means when the position exceeds the threshold position.
