A process and a degassing unit for the degassing of plastic melt in a screw extruder in which a surface of the degassing unit facing the screws of the extruder are heated to prevent deposition of entrained plastic particles, particularly at the corners or edges of the degassing unit. Prior to the commencement of the treatment process, the degassing unit is heated to a temperature which is at least as high as the melting point of the plastic to be treated. Heating can be effected by conveying a heating medium through a channel in the degassing unit located in proximity to the surface facing the extrusion screws and especially the corner or edge regions.