diff --git a/src/musrPrimaryGeneratorAction.cc b/src/musrPrimaryGeneratorAction.cc
index cc1469b..c26c29a 100644
--- a/src/musrPrimaryGeneratorAction.cc
+++ b/src/musrPrimaryGeneratorAction.cc
@@ -538,11 +538,12 @@ void musrPrimaryGeneratorAction::SetOrReadTheRandomNumberSeeds(G4Event* anEvent)
 }
 
 void musrPrimaryGeneratorAction::SetKEnergy(G4double val)  {
-  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
-  G4double mu_mass = particleTable->FindParticle("mu+")->GetPDGMass();
-  p0=std::sqrt(val*val + 2*mu_mass*val);
-  //  G4cout<<"musrPrimaryGeneratorAction::SetKEnergy: Muon kinetic energy of "
-  //	<<val<<" MeV requested ==> initial muon momentum set to "<<p0<<" MeV/c"<<G4endl;
+  //G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
+  //G4double mu_mass = particleTable->FindParticle("mu+")->GetPDGMass();
+  G4double particle_mass = particleGun->GetParticleDefinition()->GetPDGMass();
+  p0=std::sqrt(val*val + 2*particle_mass*val);
+/*   G4cout<<"musrPrimaryGeneratorAction::SetKEnergy: Particle mass " <<particle_mass<<" particle kinetic energy of "
+  	<<val<<" MeV requested ==> initial particle momentum set to "<<p0<<" MeV/c"<<G4endl;*/
 }
 
 //===============================================================================