diff --git a/src/models/flight_control/FGMagnetometer.cpp b/src/models/flight_control/FGMagnetometer.cpp
index 67219eaeb2..c2a6d892b0 100644
--- a/src/models/flight_control/FGMagnetometer.cpp
+++ b/src/models/flight_control/FGMagnetometer.cpp
@@ -102,8 +102,7 @@ FGMagnetometer::~FGMagnetometer()
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 void FGMagnetometer::updateInertialMag(void)
 {
-  counter++;
-  if (counter > INERTIAL_UPDATE_RATE)//dont need to update every iteration
+  if (counter++ % INERTIAL_UPDATE_RATE == 0)//dont need to update every iteration
   {
     counter = 0;