A method (400) for controlling a regulating valve (206) of a packaging machine (100), wherein the packaging machine (100) is a roll-fed packaging machine configured to receive a roll of a carton-based packaging material (102). The packaging machine (100) is configured to be connected to a processing line (202) via the regulating valve (206), wherein the processing line (202) is configured to feed a liquid food product (216) to the packaging machine (100) through the regulating valve (206). The method (400) comprises determining (S402) a product flow, using a flow meter (106), of the liquid food product in the packaging machine (100); determining (S404) an inlet pressure measurement (306), using a pressure sensor (204), of the liquid food product in the packaging machine (100); and making use of the inlet pressure measurement to the packaging machine (100) for adjusting the regulating valve (206), said regulating valve being configured to receive an output signal from a flow feed forward module (308) in combination with an output signal from a flow proportional-integral-derivative (PID) module (310), wherein the flow feed forward module (308) has the inlet pressure measurement (306) and a flow set point as input signals, and wherein the flow PID module (310) has the product flow and the flow set point as input signals.