The present invention is directed to a SMA valve for controlling air supply to an air cell in a vehicle seat, comprising a control unit arranged to open the valve in predetermined cycles, each cycle having predetermined activation start and stop times, by supplying an electrical activation power to a SMA wire which in turn acts on a valve element to open the valve for each cycle when the SMA wire shortens upon reaching the threshold temperature, and a temperature sensor for sensing the ambient temperature around the SMA wire. According to the invention the control unit is arranged to receive the temperature signal from the temperature sensor and to determine an activation delay time and an deactivation delay time in dependence on the temperature sensed by the temperature sensor, and to correct the activation start time and the activation stop time for the activation delay time and the deactivation delay time, respectively, to provide a corrected activation start time and a corrected activation stop time to be used for the next cycle.