diff --git a/CMakeLists.txt b/CMakeLists.txt
index d1171ccd1eedf57f0567cc2b68bcdb3b41c94115..b918904d255f5bc9d294414412a5d8fdbce23c60 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,40 +68,40 @@ add_subdirectory(DDRec)
 add_subdirectory(DDDetectors)
 
 #fg: comment out this section as it seems to conflict with Geant4 10.02.p01 and CLHEP 2.3.1.1
-#if(DD4HEP_USE_GEANT4)
-#  set ( DD4HEP_USE_CLHEP "OFF" )
-#  #--- create a geant4 variables for the thisdd4hep.sh script
-#  find_package( Geant4 9.6 REQUIRED  gdml ui_all vis_all)
-#
-#  include(${Geant4_USE_FILE})   # this also takes care of geant 4 definitions and include dirs
-#
-#  #----- if geant4 is build with external CLHEP we also need to export this fact
-#
-#  string(FIND "${Geant4_THIRD_PARTY_INCLUDE_DIRS}"  "CLHEP" CLHEP_POS )
-# 
-#  if( (NOT "${CLHEP_POS}" STREQUAL "-1") OR (NOT Geant4_builtin_clhep_FOUND)  )
-#    set( GEANT4_USE_CLHEP 1 )
-#    get_filename_component(Geant4_ROOT "${Geant4_INCLUDE_DIR}/../../" ABSOLUTE)
-#    #---- use FindCLHEP shipped with geant4 -----------
-#    set(CMAKE_MODULE_PATH  ${CMAKE_MODULE_PATH}  ${Geant4_ROOT}/cmake/Modules ) 
+if(DD4HEP_USE_GEANT4)
+  set ( DD4HEP_USE_CLHEP "OFF" )
+  #--- create a geant4 variables for the thisdd4hep.sh script
+  find_package( Geant4 9.6 REQUIRED  gdml ui_all vis_all)
+  
+  include(${Geant4_USE_FILE})   # this also takes care of geant 4 definitions and include dirs
+  
+  #----- if geant4 is build with external CLHEP we also need to export this fact
+  
+  string(FIND "${Geant4_THIRD_PARTY_INCLUDE_DIRS}"  "CLHEP" CLHEP_POS )
+  
+  if( (NOT "${CLHEP_POS}" STREQUAL "-1") OR (NOT Geant4_builtin_clhep_FOUND)  )
+    set( GEANT4_USE_CLHEP 1 )
+    get_filename_component(Geant4_ROOT "${Geant4_INCLUDE_DIR}/../../" ABSOLUTE)
+    #---- use FindCLHEP shipped with geant4 -----------
+    set(CMAKE_MODULE_PATH  ${CMAKE_MODULE_PATH}  ${Geant4_ROOT}/cmake/Modules ) 
     
-#    if( CLHEP_DIR ) #---- use 'canonical' name -----
-#      set( CLHEP_ROOT_DIR ${CLHEP_DIR} )
-#    endif()
-#
-#    find_package( CLHEP REQUIRED )
-#    include_directories( SYSTEM ${CLHEP_INCLUDE_DIRS} )
-#    set ( DD4HEP_USE_CLHEP ON )
-#
-#    get_filename_component(CLHEP_LIBRARY_PATH "${CLHEP_LIBRARIES}" PATH)
-#    message( STATUS " *** geant4 was build with external CLHEP *** CLHEP_LIBRARY_PATH = ${CLHEP_LIBRARY_PATH}"  )
-#  else()
-#    set( GEANT4_USE_CLHEP 0 )
-#  endif()
-#
-#  set(Geant4_INCLUDE_DIRS ${Geant4_INCLUDE_DIRS} ${CLHEP_INCLUDE_DIRS})
-#  set(Geant4_LIBRARIES    ${Geant4_LIBRARIES} ${CLHEP_LIBRARIES})
-#endif()
+    if( CLHEP_DIR ) #---- use 'canonical' name -----
+      set( CLHEP_ROOT_DIR ${CLHEP_DIR} )
+    endif()
+    
+    find_package( CLHEP REQUIRED )
+    include_directories( SYSTEM ${CLHEP_INCLUDE_DIRS} )
+    set ( DD4HEP_USE_CLHEP ON )
+    
+    get_filename_component(CLHEP_LIBRARY_PATH "${CLHEP_LIBRARIES}" PATH)
+    message( STATUS " *** geant4 was build with external CLHEP *** CLHEP_LIBRARY_PATH = ${CLHEP_LIBRARY_PATH}"  )
+  else()
+    set( GEANT4_USE_CLHEP 0 )
+  endif()
+  
+  set(Geant4_INCLUDE_DIRS ${Geant4_INCLUDE_DIRS} ${CLHEP_INCLUDE_DIRS})
+  set(Geant4_LIBRARIES    ${Geant4_LIBRARIES} ${CLHEP_LIBRARIES})
+endif()
 
 #------- now configure DDG4 -------
 add_subdirectory(DDG4)