diff --git a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p2.cxx b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p2.cxx
index 1918f155e1c82af4987bf52a5ccb64d99f9cbb48..a9110d0a7244479e265c42c6c3da91701f8c5cce 100755
--- a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p2.cxx
+++ b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p2.cxx
@@ -288,6 +288,7 @@ McEventCollectionCnv_p2::createGenParticle( const GenParticle_p2& persPart,
 
   // fillin' the flow
   const unsigned int nFlow = persPart.m_flow.size();
+  p->m_flow.clear();
   for ( unsigned int iFlow= 0; iFlow != nFlow; ++iFlow ) {
     p->m_flow.set_icode( persPart.m_flow[iFlow].first,
                          persPart.m_flow[iFlow].second );
diff --git a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p3.cxx b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p3.cxx
index db3e6b74e11ea73718f459c38031697143ee470f..2a8fbfe64aeed9851004daed2efe9504c916622a 100755
--- a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p3.cxx
+++ b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p3.cxx
@@ -315,6 +315,7 @@ McEventCollectionCnv_p3::createGenParticle( const GenParticle_p3& persPart,
 
   // setup flow
   const unsigned int nFlow = persPart.m_flow.size();
+  p->m_flow.clear();
   for ( unsigned int iFlow= 0; iFlow != nFlow; ++iFlow ) {
     p->m_flow.set_icode( persPart.m_flow[iFlow].first,
                          persPart.m_flow[iFlow].second );
diff --git a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p4.cxx b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p4.cxx
index 5f6ca99d72305f530b26243833083de67e45a06f..a4643fad10b698889d95e2bdc7b028550c06757a 100755
--- a/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p4.cxx
+++ b/Generators/GeneratorObjectsTPCnv/src/McEventCollectionCnv_p4.cxx
@@ -537,6 +537,7 @@ McEventCollectionCnv_p4::createGenParticle( const GenParticle_p4& persPart,
 
   // setup flow
   const unsigned int nFlow = persPart.m_flow.size();
+  p->m_flow.clear();
   for ( unsigned int iFlow= 0; iFlow != nFlow; ++iFlow )
     {
       p->m_flow.set_icode( persPart.m_flow[iFlow].first,