diff --git a/DDG4/src/Geant4GeneratorWrapper.cpp b/DDG4/src/Geant4GeneratorWrapper.cpp
index b40bec032674bf7f77a0da4eeaaea72a503367d2..858300e5f356cacfdc5c23a49323e24fa1b85363 100644
--- a/DDG4/src/Geant4GeneratorWrapper.cpp
+++ b/DDG4/src/Geant4GeneratorWrapper.cpp
@@ -70,13 +70,13 @@ void Geant4GeneratorWrapper::operator()(G4Event* event)  {
   Geant4PrimaryMap*   primaryMap = context()->event().extension<Geant4PrimaryMap>();
   set<G4PrimaryVertex*> primaries;
   
+  // Now generate the new interaction
+  generator()->GeneratePrimaryVertex(event);
+
   /// Collect all existing interactions (primary vertices)
   for(G4PrimaryVertex* v=event->GetPrimaryVertex(); v; v=v->GetNext())
     primaries.insert(v);
 
-  // Now generate the new interaction
-  generator()->GeneratePrimaryVertex(event);
-
   // Add all the missing interactions (primary vertices) to the primary event record.
   Geant4PrimaryInteraction* inter = createPrimary(m_mask, primaryMap, primaries);
   prim->add(m_mask, inter);
diff --git a/DDG4/src/Geant4InputHandling.cpp b/DDG4/src/Geant4InputHandling.cpp
index 279db4b6a2bd790638a4786c817b0be51e5e00fd..84c1a7a816be8e7740ec34cb497660753dccf209 100644
--- a/DDG4/src/Geant4InputHandling.cpp
+++ b/DDG4/src/Geant4InputHandling.cpp
@@ -88,6 +88,11 @@ static void collectPrimaries(Geant4PrimaryMap*         pm,
                              Geant4Vertex*             particle_origine,
                              G4PrimaryParticle*        gp)
 {
+  //if the particle is in the map, we do not have to do anything
+  if ( pm->get(gp) )  {
+    return;
+  }
+
   int pid = int(interaction->particles.size());
   Geant4Particle* p = createPrimary(pid,particle_origine,gp);
   G4PrimaryParticle* dau = gp->GetDaughter();