diff --git a/Simulation/ISF/ISF_Geant4/ISF_Geant4UserActions/src/FastCaloSimParamAction.cxx b/Simulation/ISF/ISF_Geant4/ISF_Geant4UserActions/src/FastCaloSimParamAction.cxx
index 3a91a35eaa3a725cb124667eb082b2fa3e8ea65b..f66e42e510ee6e8251c92d06ffa8aa63eecdc317 100644
--- a/Simulation/ISF/ISF_Geant4/ISF_Geant4UserActions/src/FastCaloSimParamAction.cxx
+++ b/Simulation/ISF/ISF_Geant4/ISF_Geant4UserActions/src/FastCaloSimParamAction.cxx
@@ -433,7 +433,7 @@ namespace G4UA{
               {
                 //if (!shortstep) G4cout <<"ZH process step ok: "<<results.size()<<G4endl;
 
-                for (auto larhit: results)
+                for (const auto& larhit: results)
                   {
                     et += larhit.energy;
                     //std::cout <<"ZH Hit: "<<i<<" E: "<<larhit.energy<<" in: "<<(std::string) larhit.id <<std::endl;