diff --git a/Tools/autotest/pysim/util.py b/Tools/autotest/pysim/util.py
index 15658fef9f..6566cfcc0f 100644
--- a/Tools/autotest/pysim/util.py
+++ b/Tools/autotest/pysim/util.py
@@ -375,8 +375,7 @@ class Wind(object):
         w_delta = math.sqrt(deltat)*(1.0-random.gauss(1.0, self.turbulance))
         w_delta -= (self.turbulance_mul-1.0)*(deltat/self.turbulance_time_constant)
         self.turbulance_mul += w_delta
-        
-        speed = self.speed * self.turbulance_mul
+        speed = self.speed * math.fabs(self.turbulance_mul)
         return (speed, self.direction)
 
     def accel(self, velocity, deltat=None):