diff --git a/mission/controller/acs/control/PtgCtrl.cpp b/mission/controller/acs/control/PtgCtrl.cpp
index 297230cf..5cbaec39 100644
--- a/mission/controller/acs/control/PtgCtrl.cpp
+++ b/mission/controller/acs/control/PtgCtrl.cpp
@@ -190,8 +190,8 @@ void PtgCtrl::ptgDesaturation(const bool allRwAvailable, const acsctrl::RwAvail
 
   // calculate total angular momentum
   double angMomentumTotal[3] = {0, 0, 0};
-  VectorOperations<double>::add(angMomentumRw, pointingLawParameters->desatMomentumRef,
-                                angMomentumTotal, 3);
+  VectorOperations<double>::subtract(angMomentumRw, pointingLawParameters->desatMomentumRef,
+                                     angMomentumTotal, 3);
 
   // resulting magnetic dipole command
   double crossAngMomentumMagField[3] = {0, 0, 0};