SITL and hexacopter, no YAW when changing frame to heaxcopter

hi all,
im trying to run SITL with a hexacopter. when i change the frame to hexacopter, the YAW is not responding. and when i change it back to quad the YAW works fine.
running ArduCopter V4.0.3.
here is my command:
./arducopte -S -I0 --home 31.8009655,34.6343780,584,353 --model “x” --speedup1 --defaults /home/aeroguardian/AeroGuardian/apm/ardupilot/Tools/autotest/default_params/copter-hexa.parm