To provide an improved wind turbine rotor blade that overcomes problems of a conventional technology.

A blade (1) comprises a thickened zone (TZ) with a thickness coefficient of at least 0.45 extending outward from a root portion (10) into an airfoil portion (19) of the blade (1). An airflow correction arrangement (2, 3) is arranged on a pressure side (11) of the blade (1) over at least a portion of the thickened zone (TZ). The airflow correction arrangement (2, 3) comprises a spoiler (3) and a vortex generator (2). The vortex generator (2) is arranged to maintain an attached airflow (42) between the vortex generator (2) and the spoiler (3).