diff --git a/src/Tools/RivetHepMC_3.cc b/src/Tools/RivetHepMC_3.cc
--- a/src/Tools/RivetHepMC_3.cc
+++ b/src/Tools/RivetHepMC_3.cc
@@ -1,83 +1,83 @@
 // -*- C++ -*-
 
 #include "Rivet/Tools/RivetHepMC.hh"
 #include "HepMC3/ReaderAscii.h"
 #include "HepMC3/ReaderAsciiHepMC2.h"
 
 namespace Rivet{
   
   namespace HepMCUtils{
     
     std::vector<ConstGenParticlePtr> particles(ConstGenEventPtr ge){
       return ge->particles();
     }
     
     std::vector<ConstGenParticlePtr> particles(const GenEvent *ge){
       assert(ge);
       return ge->particles();
     }
     
     std::vector<ConstGenVertexPtr> vertices(ConstGenEventPtr ge){
       return ge->vertices();
     }
     
     std::vector<ConstGenVertexPtr> vertices(const GenEvent *ge){
       assert(ge);
       return ge->vertices();
     }
     
     std::vector<ConstGenParticlePtr> particles(ConstGenVertexPtr gv, const Relatives &relo){
       return relo(gv);
     }
     
     std::vector<ConstGenParticlePtr> particles(ConstGenParticlePtr gp, const Relatives &relo){
       return relo(gp);
     }
     
     int uniqueId(ConstGenParticlePtr gp){
       return gp->id();
     }
     
     std::vector<ConstGenParticlePtr> beams(const GenEvent *ge){
       return ge->beams();
     }
     
     bool readEvent(std::shared_ptr<HepMC_IO_type> io, std::shared_ptr<GenEvent> evt){
       io->read_event(*evt);
       return !io->failed();
     }
     
     shared_ptr<HepMC_IO_type> makeReader(std::istream &istr){
       if(&istr == &std::cin) return make_shared<RivetHepMC::ReaderAsciiHepMC2>(istr);
       
       istr.seekg(istr.beg);
       std::string line1, line2;
       
       while(line1.empty()){
         std::getline(istr, line1);
       }
       
       while(line2.empty()){
         std::getline(istr, line2);
       }
       
       istr.seekg(istr.beg);
       
       // if this is absent it doesn't appear to be a HepMC file :(
       if(line1.find("HepMC::Version") == std::string::npos) return nullptr;
       
       shared_ptr<HepMC_IO_type> result;
       
       // Looks like the new HepMC 3 format!
       if(line2.find("HepMC::Asciiv3") != std::string::npos){
         result = make_shared<RivetHepMC::ReaderAscii>(istr);
+      }else{
+        // assume old HepMC 2 format from here
+        result = make_shared<RivetHepMC::ReaderAsciiHepMC2>(istr);
       }
       
-      // assume old HepMC 2 format from here
-      result = make_shared<RivetHepMC::ReaderAsciiHepMC2>(istr);
-      
       if(result->failed()) result.reset((RivetHepMC::Reader*)nullptr);
       return result;
     }
   }
 }