diff --git a/mission/controller/acs/SensorProcessing.cpp b/mission/controller/acs/SensorProcessing.cpp
index a8fd1576..5b4ddc84 100644
--- a/mission/controller/acs/SensorProcessing.cpp
+++ b/mission/controller/acs/SensorProcessing.cpp
@@ -129,6 +129,7 @@ void SensorProcessing::processMgm(const float *mgm0Value, bool mgm0valid, const
     for (uint8_t i = 0; i < 3; i++) {
       mgmVecTotDerivative[i] = (mgmVecTot[i] - savedMgmVecTot[i]) / timeDiff;
       savedMgmVecTot[i] = mgmVecTot[i];
+      mgmVecTotDerivativeValid = true;
     }
   }
   timeOfSavedMagFieldEst = timeOfMgmMeasurement;