diff --git a/SimDataFormats/GeneratorProducts/interface/HepMC3Product.h b/SimDataFormats/GeneratorProducts/interface/HepMC3Product.h
index fb8b72e71ac2f..37e1ab54e6f28 100644
--- a/SimDataFormats/GeneratorProducts/interface/HepMC3Product.h
+++ b/SimDataFormats/GeneratorProducts/interface/HepMC3Product.h
@@ -23,10 +23,10 @@ namespace edm {
   public:
     HepMC3Product() : isVtxGenApplied_(false), isVtxBoostApplied_(false), isPBoostApplied_(false) {}
 
-    explicit HepMC3Product(HepMC3::GenEvent *evt);
+    explicit HepMC3Product(const HepMC3::GenEvent *evt);
     ~HepMC3Product();
 
-    void addHepMCData(HepMC3::GenEvent *evt);
+    void addHepMCData(const HepMC3::GenEvent *evt);
 
     void applyVtxGen(HepMC3::FourVector const *vtxShift) { applyVtxGen(*vtxShift); }
     void applyVtxGen(HepMC3::FourVector const &vtxShift);
diff --git a/SimDataFormats/GeneratorProducts/src/HepMC3Product.cc b/SimDataFormats/GeneratorProducts/src/HepMC3Product.cc
index f39cdb4c9940b..e48d6adc33329 100644
--- a/SimDataFormats/GeneratorProducts/src/HepMC3Product.cc
+++ b/SimDataFormats/GeneratorProducts/src/HepMC3Product.cc
@@ -16,14 +16,14 @@
 using namespace edm;
 using namespace std;
 
-HepMC3Product::HepMC3Product(HepMC3::GenEvent* evt)
+HepMC3Product::HepMC3Product(const HepMC3::GenEvent* evt)
     : isVtxGenApplied_(false), isVtxBoostApplied_(false), isPBoostApplied_(false) {
   addHepMCData(evt);
 }
 
 HepMC3Product::~HepMC3Product() = default;
 
-void HepMC3Product::addHepMCData(HepMC3::GenEvent* evt) { evt->write_data(evt_); }
+void HepMC3Product::addHepMCData(const HepMC3::GenEvent* evt) { evt->write_data(evt_); }
 
 void HepMC3Product::applyVtxGen(HepMC3::FourVector const& vtxShift) {
   //std::cout<< " applyVtxGen called " << isVtxGenApplied_ << endl;