diff --git a/MuonSpectrometer/MuonTruthAlgs/src/MuonTruthDecorationAlg.cxx b/MuonSpectrometer/MuonTruthAlgs/src/MuonTruthDecorationAlg.cxx
index 065c635b3357e75f4c22976c573f8b464a412b3a..9d8879ac8de9fd36a3328b4dd31a5302ec817baa 100644
--- a/MuonSpectrometer/MuonTruthAlgs/src/MuonTruthDecorationAlg.cxx
+++ b/MuonSpectrometer/MuonTruthAlgs/src/MuonTruthDecorationAlg.cxx
@@ -467,6 +467,13 @@ namespace Muon {
         }
       }
     }
+    std::vector<float> emptyVec;
+    for( const auto& col : trackRecords ){
+      const std::string name = col.second;
+      if(!truthParticle.isAvailable<std::vector<float> >(name+"_cov_extr")){
+	truthParticle.auxdata<std::vector<float> >(name+"_cov_extr")=emptyVec;
+      }
+    }
   }