The invention concerns an arrangement for mounting a single-piece windscreen wiper arm (10) on a head (12) driving the arm (10) in a reciprocating sweeping movement, wherein the arm (10) comprises a first mounting end (10a) which is connected to the driving head (12) so as to transmit the sweeping forces driving the arm (10) and wherein the first end (10a) of the arm (10) is mounted mobile relative to the driving head (12) between a lowered wiping position wherein the blade is pressed against the glass pane and a raised position wherein the blade is spaced apart from the glass pane. The invention is characterized in that it comprises means for locking the first end (10a) of the arm (10) in lowered position, which are adapted to change state when a lifting force is exerted on the arm (10), to enable the first end (10a) of the arm (10) to be moved towards the raised position.