diff --git a/DDG4/CMakeLists.txt b/DDG4/CMakeLists.txt
index fa490ee1cd5ce641e4658dbee837d6fb8efe5766..b416a8f9b5800d032bcd05936901c991db254cad 100644
--- a/DDG4/CMakeLists.txt
+++ b/DDG4/CMakeLists.txt
@@ -14,6 +14,7 @@ endif()
 include_directories(${CMAKE_SOURCE_DIR}/DDCore/include
                     ${CMAKE_CURRENT_SOURCE_DIR}/include 
                     ${ROOT_INCLUDE_DIR}
+                    ${CLHEP_INCLUDE_DIR}
                     ${Geant4_INCLUDE_DIRS}
                     ${XERCESC_INCLUDE_DIR})