diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5751210..7ebac76 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,10 @@ list(APPEND CMAKE_PREFIX_PATH $ENV{ROOTSYS}) ############USEROOTSYS
 
 find_package(ROOT REQUIRED COMPONENTS Proof)  ###########USEROOTSYS
 
+#give clas12root include dir
+set(CLAS12ROOT_DIR $ENV{CLAS12ROOT}/Clas12Root)
+include_directories(${CLAS12ROOT_DIR})
+
 #---Define useful ROOT functions and macros (e.g. ROOT_GENERATE_DICTIONARY)
 include(${ROOT_USE_FILE}) ##########USEROOTSYS
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ROOT_CXX_FLAGS}")