diff --git a/analyzers/dataframe/VertexFitterActs.cc b/analyzers/dataframe/VertexFitterActs.cc
index 322741fcd7..d88451a8d2 100644
--- a/analyzers/dataframe/VertexFitterActs.cc
+++ b/analyzers/dataframe/VertexFitterActs.cc
@@ -18,7 +18,6 @@
 
 using namespace VertexFitterActs;
 using namespace Acts::UnitLiterals;
-using namespace ReconstructedParticle2Track;
 
 
 VertexingUtils::FCCAnalysesVertex VertexFitterActs::VertexFitterFullBilloir(ROOT::VecOps::RVec<edm4hep::ReconstructedParticleData> recoparticles,
@@ -134,18 +133,6 @@ VertexingUtils::FCCAnalysesVertex VertexFitterActs::VertexFitterFullBilloir(ROOT
     tracksPtr.push_back(&trk);
   }
 
-  
-  Acts::Vertex<Acts::BoundTrackParameters> fittedVertex =  
-    billoirFitter.fit(tracksPtr, linearizer, vfOptions, state).value();
-  //Acts::Vertex<Acts::BoundTrackParameters> fittedVertexConstraint = 
-  //  billoirFitter.fit(tracksPtr, linearizer, vfOptionsConstr, state).value();
-
-
-  //std::cout << "Fitting nTracks: " << Ntr << std::endl;
-  //  std::cout << "Fitted Vertex: " << fittedVertex.position() << std::endl;
-  //  std::cout << "Fitted constraint Vertex: "
-  //             << fittedVertexConstraint.position() << std::endl;
-
   VertexingUtils::FCCAnalysesVertex TheVertex;
   edm4hep::VertexData edm4hep_vertex;
   ROOT::VecOps::RVec<float> reco_chi2;
@@ -162,6 +149,23 @@ VertexingUtils::FCCAnalysesVertex VertexFitterActs::VertexFitterFullBilloir(ROOT
   TheVertex.updated_track_momentum_at_vertex = updated_track_momentum_at_vertex;
 
 
+  TheVertex.ntracks = Ntr; 
+  if ( Ntr <= 1) return TheVertex;   // can not reconstruct a vertex with only one track...
+
+
+  Acts::Vertex<Acts::BoundTrackParameters> fittedVertex =  
+    billoirFitter.fit(tracksPtr, linearizer, vfOptions, state).value();
+  //Acts::Vertex<Acts::BoundTrackParameters> fittedVertexConstraint = 
+  //  billoirFitter.fit(tracksPtr, linearizer, vfOptionsConstr, state).value();
+
+
+  //std::cout << "Fitting nTracks: " << Ntr << std::endl;
+  //  std::cout << "Fitted Vertex: " << fittedVertex.position() << std::endl;
+  //  std::cout << "Fitted constraint Vertex: "
+  //             << fittedVertexConstraint.position() << std::endl;
+
+
+
   TheVertex.ntracks = Ntr;
   edm4hep_vertex.chi2 = fittedVertex.fitQuality().first/ fittedVertex.fitQuality().second ;   
   edm4hep_vertex.position = edm4hep::Vector3f( fittedVertex.position()[0],
diff --git a/analyzers/dataframe/VertexFitterSimple.cc b/analyzers/dataframe/VertexFitterSimple.cc
index 050813d5aa..c518dbacc2 100644
--- a/analyzers/dataframe/VertexFitterSimple.cc
+++ b/analyzers/dataframe/VertexFitterSimple.cc
@@ -7,8 +7,6 @@
 
 using namespace VertexFitterSimple;
 
-using namespace ReconstructedParticle2Track;
-
 
 
 
diff --git a/examples/FCCee/vertex/analysis.py b/examples/FCCee/vertex/analysis.py
index 9f0a38da39..2ff9829186 100644
--- a/examples/FCCee/vertex/analysis.py
+++ b/examples/FCCee/vertex/analysis.py
@@ -30,14 +30,14 @@ def __init__(self, inputlist, outname, ncpu):
         if ".root" not in outname:
             self.outname+=".root"
 
-        #ROOT.ROOT.EnableImplicitMT(ncpu)
+        ROOT.ROOT.EnableImplicitMT(ncpu)
 
         self.df = ROOT.RDataFrame("events", inputlist)
         print (" done")
     #__________________________________________________________
     def run(self):
-        df2 = (self.df.Range(0,5000)
-        #df2 = (self.df
+        #df2 = (self.df.Range(0,5000)
+        df2 = (self.df
 
                # MC event primary vertex
                .Define("MC_PrimaryVertex",  "MCParticle::get_EventPrimaryVertex(21)( Particle )" )
@@ -117,7 +117,7 @@ def run(self):
     import os
     os.system("mkdir -p {}".format(outDir))
     outfile = outDir+infile.split('/')[-1]
-    ncpus = 1
+    ncpus = 0
     analysis = analysis(infile, outfile, ncpus)
     analysis.run()