diff --git a/NPLib/Detectors/GeTAMU/TGeTAMUPhysics.cxx b/NPLib/Detectors/GeTAMU/TGeTAMUPhysics.cxx
index a8c6e55eab1f8cb3d448a73f1ebaa31715864932..521f518c788e4ac0649eee6153e75537693c8bd1 100644
--- a/NPLib/Detectors/GeTAMU/TGeTAMUPhysics.cxx
+++ b/NPLib/Detectors/GeTAMU/TGeTAMUPhysics.cxx
@@ -380,7 +380,7 @@ TVector3 TGeTAMUPhysics::GetPositionOfInteraction(unsigned int& i){
 // original energy, position, beta
 double TGeTAMUPhysics::GetDopplerCorrectedEnergy(double& energy , TVector3 direction, TVector3& beta){
   // renormalise pos vector
-  position.SetMag(1);
+  direction.SetMag(1);
   m_GammaLV.SetPx(energy*direction.X());
   m_GammaLV.SetPy(energy*direction.Y());
   m_GammaLV.SetPz(energy*direction.Z());