diff --git a/Control/AthToolSupport/AsgTools/AsgTools/CLASS_DEF.h b/Control/AthToolSupport/AsgTools/AsgTools/CLASS_DEF.h
deleted file mode 100644
index 27f312d25c86cda082214214fc7c6a65f4442d37..0000000000000000000000000000000000000000
--- a/Control/AthToolSupport/AsgTools/AsgTools/CLASS_DEF.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
-  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
-*/
-
-// David Adams
-// January 2014
-//
-// Wrapper for Athena CLASS_DEF macro.
-// Ignores the macro in other environments.
-//
-// Note that the clid command can be used to generate the class ID:
-//   clid -m MyClassName
-
-// Set this flag to show calls to CLASS_DEF in stanadlone environments.
-//#define CLASSDEF_SHOWDEFS
-#ifndef XAOD_STANDALONE
-  #undef CLASSDEF_SHOWDEFS
-#endif
-
-#ifdef CLASSDEF_SHOWDEFS
-#include <iostream>
-int announce(const char* name, int clid) {
-  std::cout << "*********************** Loading clid for " << name << ": " << clid << std::endl;
-  return clid;
-}
-#endif
-
-#ifndef XAOD_STANDALONE
-  #include "AthenaKernel/CLASS_DEF.h"
-#else
-  #ifdef CLASSDEF_SHOWDEFS
-    #define CLASS_DEF(NAME, CLID, VER) int clid_CLASS = announce(#NAME, CLID);
-  #else
-    // Do not define macro if someone else has already done so.
-    #ifndef CLASS_DEF
-      #define CLASS_DEF(NAME, CLID, VER)
-    #endif
-  #endif
-#endif
diff --git a/Event/xAOD/xAODCore/xAODCore/CLASS_DEF.h b/Event/xAOD/xAODCore/xAODCore/CLASS_DEF.h
index e878963015866b73a8fabb2161e15485880c448d..45cd2c9bec0dc415443094a6c49c6413f76ca3ed 100644
--- a/Event/xAOD/xAODCore/xAODCore/CLASS_DEF.h
+++ b/Event/xAOD/xAODCore/xAODCore/CLASS_DEF.h
@@ -38,10 +38,6 @@
 // Include the ClassID_traits class:
 #include "xAODCore/ClassID_traits.h"
 
-// Make sure that we get rid of the definitions from other places.
-// From AsgTools for instance...
-#undef CLASS_DEF
-
 // Present a dummy macro to ROOT 6's dictionary generator. Otherwise
 // it becomes over-eager, and starts generating dictionaries for types
 // that it should just ignore.
diff --git a/PhysicsAnalysis/Algorithms/SystematicsHandles/SystematicsHandles/SysListType.h b/PhysicsAnalysis/Algorithms/SystematicsHandles/SystematicsHandles/SysListType.h
index 57f7c8705b4d418d15af1509610130fd27aef766..bd524fac007694516b87c0963ea664e3f7be7eeb 100644
--- a/PhysicsAnalysis/Algorithms/SystematicsHandles/SystematicsHandles/SysListType.h
+++ b/PhysicsAnalysis/Algorithms/SystematicsHandles/SystematicsHandles/SysListType.h
@@ -10,7 +10,7 @@
 
 #include <string>
 #include <vector>
-#include <AsgTools/CLASS_DEF.h>
+#include <xAODCore/CLASS_DEF.h>
 
 namespace CP
 {
diff --git a/Reconstruction/Jet/JetEDM/JetEDM/ClusterSequence.h b/Reconstruction/Jet/JetEDM/JetEDM/ClusterSequence.h
index 1a686eef5faceab852b6e305b6f89634f725f7d3..5d1274a68708a26b9aac12b638076c0ea5b223cc 100644
--- a/Reconstruction/Jet/JetEDM/JetEDM/ClusterSequence.h
+++ b/Reconstruction/Jet/JetEDM/JetEDM/ClusterSequence.h
@@ -9,7 +9,7 @@
 
 #include <vector>
 #include "fastjet/ClusterSequence.hh"
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 
 // David Adams
 // January 2014
diff --git a/Reconstruction/Jet/JetEDM/JetEDM/LabelIndex.h b/Reconstruction/Jet/JetEDM/JetEDM/LabelIndex.h
index fa3bfdf348f23be73b21c29950ba1aca1beeecaa..a054101619d91e3347ffb81b0312506c8ae1119d 100644
--- a/Reconstruction/Jet/JetEDM/JetEDM/LabelIndex.h
+++ b/Reconstruction/Jet/JetEDM/JetEDM/LabelIndex.h
@@ -14,7 +14,7 @@
 
 #include <vector>
 #include <string>
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 #include "xAODJet/JetTypes.h"
 
 namespace jet {
diff --git a/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetMap.h b/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetMap.h
index 33ace318f9934720abb3cd096a22c8e4f1eb97a0..29fe1dd7b32ea47ded6e9a0c50e97c5a47d524ae 100644
--- a/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetMap.h
+++ b/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetMap.h
@@ -9,7 +9,7 @@
 
 #include <map>
 #include "fastjet/PseudoJet.hh"
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 #include "xAODJet/Jet.h"
 
 // David Adams
diff --git a/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetVector.h b/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetVector.h
index 06cfba255a587d63dd2aa273f5f087eb2acf9faf..d7ef621c64c1c500e0c1ef7235a5e5c258a756ec 100644
--- a/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetVector.h
+++ b/Reconstruction/Jet/JetEDM/JetEDM/PseudoJetVector.h
@@ -9,7 +9,7 @@
 
 #include <vector>
 #include "fastjet/PseudoJet.hh"
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 
 // David Adams
 // January 2014
diff --git a/Reconstruction/Jet/JetEDM/JetEDM/TrackVertexAssociation.h b/Reconstruction/Jet/JetEDM/JetEDM/TrackVertexAssociation.h
index a8bfe3cde511401436e0d66ae6fa4fd6958ee332..29593af15769a7d2affc111d2e9df7717db87900 100644
--- a/Reconstruction/Jet/JetEDM/JetEDM/TrackVertexAssociation.h
+++ b/Reconstruction/Jet/JetEDM/JetEDM/TrackVertexAssociation.h
@@ -12,7 +12,7 @@
 #include "xAODTracking/Vertex.h"
 #include "xAODTracking/TrackParticle.h"
 #include "xAODTracking/TrackParticleContainer.h"
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 
 namespace jet {
   
diff --git a/Reconstruction/Jet/JetRecCalo/JetRecCalo/MissingCellListTool.h b/Reconstruction/Jet/JetRecCalo/JetRecCalo/MissingCellListTool.h
index 7eb602783503f064a318bded63724ec72eb5cf34..ad26c4c32c1e5869dddf1165c339e97f29bd2a9e 100644
--- a/Reconstruction/Jet/JetRecCalo/JetRecCalo/MissingCellListTool.h
+++ b/Reconstruction/Jet/JetRecCalo/JetRecCalo/MissingCellListTool.h
@@ -40,7 +40,7 @@
 
 #include "JetUtils/TiledEtaPhiMap.h"
 
-#include "AsgTools/CLASS_DEF.h"
+#include "xAODCore/CLASS_DEF.h"
 #include "AsgTools/AsgTool.h"
 #include "JetInterface/IJetExecuteTool.h"