Disclosed is a supervision device (9) for supervising liquid drug flow in a flow channel (20). The supervision device (9) includes a flow detector (1), arranged for operatively coupling with the flow channel (20) and generating a flow detector signal in dependence of a flow in the flow channel (20) at a flow detection location. The supervision device (9) further includes a gas detector (8), arranged for operatively coupling with the flow channel (20) and generating a gas detector signal in dependence of whether liquid drug or gas is present in the flow channel (20) at a gas detection location at a distance upstream from the flow detection location. The supervision device (9) further includes a processing unit (90) in operative coupling with the flow detector (1) and the gas detector (8), wherein the processing unit (90) is configured to determine, based on a the gas detector signal, whether non-flowing liquid drug is present at the flow detection location or a gas bubble passes the flow detector if the flow detector signal does not indicate a liquid drug flow.
