A reference conditioning algorithm based on variable structure systems theory is developed to cope with actuator saturation. This sliding mode conditioning presents some distinctive features. In fact, the proposed compensation shapes a realizable reference, thus completely avoiding saturation. Then, the closed loop never leaves its prescribed linear behavior. Furthermore, as a consequence of this property as well as of the robustness features of sliding mode control, the conditioning circuit dynamics can be designed independently of the main loop dynamics. Although the paper mainly focuses on antiwindup compensation, the proposed conditioning algorithm can be exploited to address other problems of constrained processes control.