diff --git a/Tracking/include/Tracking/Event/Track.h b/Tracking/include/Tracking/Event/Track.h
index 872d120a1..b51cae3a1 100644
--- a/Tracking/include/Tracking/Event/Track.h
+++ b/Tracking/include/Tracking/Event/Track.h
@@ -248,7 +248,7 @@ class Track {
   std::vector<TrackState> trackStates_;
 
   /// Class declaration needed by the ROOT dictionary.
-  ClassDef(Track, 1);
+  ClassDef(Track, 2);
 
 };  // Track
 
diff --git a/Tracking/include/Tracking/Event/TruthTrack.h b/Tracking/include/Tracking/Event/TruthTrack.h
index cd34b11b7..10737c8d8 100644
--- a/Tracking/include/Tracking/Event/TruthTrack.h
+++ b/Tracking/include/Tracking/Event/TruthTrack.h
@@ -172,7 +172,7 @@ class TruthTrack {
   int pdgID_{0};
 
   /// Class declaration needed by the ROOT dictionary.
-  ClassDef(TruthTrack, 1);
+  ClassDef(TruthTrack, 2);
 
 };  // TruthTrack