diff --git a/cmake/DD4hepBuild.cmake b/cmake/DD4hepBuild.cmake
index 39350e7f0316b84859242c250ac17efa8be65d9b..4383f00be2b20e5e50c0beb3a07e00be2e53cc16 100644
--- a/cmake/DD4hepBuild.cmake
+++ b/cmake/DD4hepBuild.cmake
@@ -1464,8 +1464,8 @@ function ( fill_dd4hep_library_path )
 
   string(REGEX REPLACE "/lib/libCore.*" "" ROOT_ROOT ${ROOT_Core_LIBRARY})
   SET( ENV{DD4HEP_LIBRARY_PATH} ${ROOT_ROOT}/lib )
-  if ( ${} )
-    SET( ENV{DD4HEP_LIBRARY_PATH} ${BOOST_LIBRARYDIR}:$ENV{DD4HEP_LIBRARY_PATH} )
+  if ( ${Boost_LIBRARY_DIR} )
+    SET( ENV{DD4HEP_LIBRARY_PATH} ${Boost_LIBRARY_DIR}:$ENV{DD4HEP_LIBRARY_PATH} )
   endif()
   if ( ${DD4HEP_USE_GEANT4} )
     string(REGEX REPLACE "/lib/Geant4.*" "" Geant4_ROOT ${Geant4_DIR})