A method of retrofitting vortex generators on a wind turbine blade is disclosed, the wind turbine blade being mounted on a wind turbine hub and extending in a longitudinal direction and having a tip end and a root end, the wind turbine blade further comprising a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift. The method comprises identifying a separation line on the suction side of the wind turbine blade, and mounting one or more vortex panels including a first vortex panel comprising at least one vortex generator on the suction side of the wind turbine blade between the separation line and the leading edge of the wind turbine blade.