diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d4da7e79f209fc2101e4307a19c00a91a4d4cdf6..7c20992593067a2ee7a7e8f6d2021bdaf86b383b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -12,7 +12,7 @@ slc6-gcc48:
     - source .gitlab-ci.d/init_x86_64-slc6-gcc48-opt.sh
     - mkdir build 
     - cd build
-    - cmake -D DD4HEP_USE_GEANT4=1 -D DD4HEP_USE_BOOST=ON -DBoost_NO_BOOST_CMAKE=ON -D DD4HEP_USE_LCIO=ON -D BUILD_TESTING=ON -D CLHEP_DIR=$CLHEP -DCMAKE_CXX_COMPILER=`which g++` -DCMAKE_C_COMPILER=`which gcc` ..
+    - cmake -D DD4HEP_USE_GEANT4=1 -D DD4HEP_USE_BOOST=ON -DBoost_NO_BOOST_CMAKE=ON -D DD4HEP_USE_LCIO=ON -D BUILD_TESTING=ON -D CLHEP_DIR=$CLHEP -DCMAKE_CXX_COMPILER=`which g++` -DCMAKE_C_COMPILER=`which gcc` -D Geant4_DIR=$G4INSTALL/lib64/Geant4-10.1.2 ..
     - make -j4
     - make install
 
@@ -25,6 +25,6 @@ slc6-gcc49:
     - source .gitlab-ci.d/init_x86_64-slc6-gcc49-opt.sh
     - mkdir build 
     - cd build
-    - cmake -D DD4HEP_USE_GEANT4=1 -D DD4HEP_USE_BOOST=ON -DBoost_NO_BOOST_CMAKE=ON -D DD4HEP_USE_LCIO=ON -D BUILD_TESTING=ON -D CLHEP_DIR=$CLHEP -DCMAKE_CXX_COMPILER=`which g++` -DCMAKE_C_COMPILER=`which gcc` ..
+    - cmake -D DD4HEP_USE_GEANT4=1 -D DD4HEP_USE_BOOST=ON -DBoost_NO_BOOST_CMAKE=ON -D DD4HEP_USE_LCIO=ON -D BUILD_TESTING=ON -D CLHEP_DIR=$CLHEP -DCMAKE_CXX_COMPILER=`which g++` -DCMAKE_C_COMPILER=`which gcc` -D Geant4_DIR=$G4INSTALL/lib64/Geant4-10.1.2 ..
     - make -j4
     - make install