diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5220985e..db8ff779 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,9 @@ will consitute of a breaking change warranting a new major release:
 
 - `PDEC_CONFIG_CORRUPTED` event now actually contains the readback instead of the expected
   config
+- Magnetic field vector was not calculated if only MGM4 was available, but still written to
+  the dataset. This would result in a NaN vector. Allowance for usage of MGM4 is now checked
+  before entering calculation.
 
 # [v6.4.0] 2023-08-16
 
diff --git a/mission/controller/acs/SensorProcessing.cpp b/mission/controller/acs/SensorProcessing.cpp
index 686a2fcf..4405790c 100644
--- a/mission/controller/acs/SensorProcessing.cpp
+++ b/mission/controller/acs/SensorProcessing.cpp
@@ -25,7 +25,8 @@ void SensorProcessing::processMgm(const float *mgm0Value, bool mgm0valid, const
                         gpsDataProcessed->altitude.value, timeOfMgmMeasurement, magIgrfModel);
     gpsValid = true;
   }
-  if (!mgm0valid && !mgm1valid && !mgm2valid && !mgm3valid && !mgm4valid) {
+  if (not mgm0valid and not mgm1valid and not mgm2valid and not mgm3valid and
+      (not mgm4valid or not mgmParameters->useMgm4)) {
     {
       PoolReadGuard pg(mgmDataProcessed);
       if (pg.getReadResult() == returnvalue::OK) {