diff --git a/k4Reco/ConformalTracking/components/ConformalTracking.cpp b/k4Reco/ConformalTracking/components/ConformalTracking.cpp
index 8fbabf13..3d75d8a6 100644
--- a/k4Reco/ConformalTracking/components/ConformalTracking.cpp
+++ b/k4Reco/ConformalTracking/components/ConformalTracking.cpp
@@ -1761,7 +1761,7 @@ void ConformalTracking::extendTracksPerLayer(UniqueKDTracks& conformalTracks, Sh
           deltaChi2zs = newchi2zs - chi2zs;
           debug() << "-- hit was fitted and has a delta chi2 of " << deltaChi2 << " and delta chi2zs of " << deltaChi2zs
                   << endmsg;
-          tempTrack.remove(tempTrack.m_clusters.size());
+          tempTrack.remove(tempTrack.m_clusters.size() - 1);
           debug() << "-- tempTrack has now " << tempTrack.m_clusters.size() << " hits " << endmsg;
 
           double chi2cut = parameters.m_chi2cut;
diff --git a/k4Reco/ConformalTracking/include/KDTrack.h b/k4Reco/ConformalTracking/include/KDTrack.h
index 24ccd10c..08d9b059 100644
--- a/k4Reco/ConformalTracking/include/KDTrack.h
+++ b/k4Reco/ConformalTracking/include/KDTrack.h
@@ -22,8 +22,8 @@
 #include "KDCluster.h"
 #include "Parameters.h"
 
-#include <cmath>
 #include <memory>
+#include <stdexcept>
 #include <vector>
 
 class TH2F;
@@ -50,7 +50,12 @@ class KDTrack {
   //--- Functions to add and remove clusters
   void add(SKDCluster cluster) { m_clusters.push_back(cluster); }
   void insert(SKDCluster cluster) { m_clusters.insert(m_clusters.begin(), cluster); }
-  void remove(int clusterN) { m_clusters.erase(m_clusters.begin() + clusterN); }
+  void remove(int clusterN) {
+    if (clusterN < 0 || clusterN >= static_cast<int>(m_clusters.size())) {
+      throw std::out_of_range("KDTrack::remove: clusterN out of range");
+    }
+    m_clusters.erase(m_clusters.begin() + clusterN);
+  }
 
   //--- Fit functions
   double calculateChi2();