diff --git a/cmake/thisdd4hep.sh b/cmake/thisdd4hep.sh
index 6095e76a77d893844ae1206726665e19a8447b1c..8ce2bb4af6c9c26f6b11d18c70558341e71affc9 100644
--- a/cmake/thisdd4hep.sh
+++ b/cmake/thisdd4hep.sh
@@ -82,6 +82,7 @@ if [ ${Geant4_DIR} ]; then
     #---- if geant4 was built with external CLHEP we have to extend the dynamic search path
     if [ @GEANT4_USE_CLHEP@ ] ; then
 	dd4hep_add_library_path @CLHEP_LIBRARY_PATH@;
+	export CLHEP_DIR=@CLHEP_DIR@
     fi;
     dd4hep_add_library_path ${G4LIB_DIR};
     unset G4ENV_INIT;