diff --git a/include/KDTrack.h b/include/KDTrack.h
index 7e89f5d..5cc8fdc 100644
--- a/include/KDTrack.h
+++ b/include/KDTrack.h
@@ -5,6 +5,7 @@
 #include "Parameters.h"
 
 #include <cmath>
+#include <stdexcept>
 
 class TH2F;
 
@@ -35,6 +36,9 @@ class KDTrack {
     m_nPoints++;
   }
   void remove(int clusterN) {
+    if(clusterN < 0 || clusterN >= int(m_clusters.size())) {
+      throw std::out_of_range("KDTrack::remove: clusterN out of range");
+    }
     m_clusters.erase(m_clusters.begin() + clusterN);
     m_nPoints--;
   }
diff --git a/src/ConformalTracking.cc b/src/ConformalTracking.cc
index 26aca9b..36ecff0 100644
--- a/src/ConformalTracking.cc
+++ b/src/ConformalTracking.cc
@@ -2049,7 +2049,7 @@ void ConformalTracking::extendTracksPerLayer(UniqueKDTracks& conformalTracks, Sh
           deltaChi2zs = newchi2zs - chi2zs;
           streamlog_out(DEBUG9) << "-- hit was fitted and has a delta chi2 of " << deltaChi2 << " and delta chi2zs of "
                                 << deltaChi2zs << std::endl;
-          tempTrack.remove(tempTrack.m_clusters.size());
+          tempTrack.remove(tempTrack.m_clusters.size() - 1);
           streamlog_out(DEBUG9) << "-- tempTrack has now " << tempTrack.m_clusters.size() << " hits " << std::endl;
 
           double chi2cut = parameters._chi2cut;