diff --git a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/ITrkVKalVrtFitter.h b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/ITrkVKalVrtFitter.h
index 33c7a25f3b2730a7c215b9d88e0fd5b5fbaf47ec..097eec118c34ef50426f730eea6bc49fcb8035d4 100755
--- a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/ITrkVKalVrtFitter.h
+++ b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/ITrkVKalVrtFitter.h
@@ -113,7 +113,7 @@ namespace Trk{
       virtual void setVertexForConstraint(double,double,double)=0;
       virtual void setCovVrtForConstraint(double,double,double,
                                           double,double,double)=0;
-      virtual void setMassInputParticles( std::vector<double>& )=0;
+      virtual void setMassInputParticles( const std::vector<double>& )=0;
       virtual void setDefault() =0;
       virtual void setZeroCharge(int)=0;
 //
diff --git a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/TrkVKalVrtFitter.h b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/TrkVKalVrtFitter.h
index 836c0609e41729c6c7a569c9595684af8780280b..4462cd5ebe29ab5d7d25678f921bc28ff33ae258 100755
--- a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/TrkVKalVrtFitter.h
+++ b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/TrkVKalVrtFitter.h
@@ -225,7 +225,7 @@ namespace Trk{
         void setCovVrtForConstraint(double,double,double,
                                   double,double,double);
 				  
-        void setMassInputParticles( std::vector<double>& );
+        void setMassInputParticles( const std::vector<double>& );
         void setMomCovCalc(int);
         void setDefault();
         void setZeroCharge(int);
diff --git a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/src/SetFitOptions.cxx b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/src/SetFitOptions.cxx
index 4f51122235f9a914bd6991c80210c06288f477a8..2bb7cf1a48b160bbf1c2f567b0f7e0275491e1bb 100755
--- a/Tracking/TrkVertexFitter/TrkVKalVrtFitter/src/SetFitOptions.cxx
+++ b/Tracking/TrkVertexFitter/TrkVKalVrtFitter/src/SetFitOptions.cxx
@@ -217,7 +217,7 @@ namespace Trk{
      m_CovVrtForConstraint.push_back(ZZ);
   }			  
 
-  void TrkVKalVrtFitter::setMassInputParticles( std::vector<double>& mass)
+  void TrkVKalVrtFitter::setMassInputParticles( const std::vector<double>& mass)
   { m_MassInputParticles.clear();
     for(int i=0; i<(int)mass.size(); i++) m_MassInputParticles.push_back(fabs(mass[i]));
   }