diff --git a/CMakeLists.txt b/CMakeLists.txt
index 199e75208ef96eb7bc05442d36fb30ab57883694..d54ae447694ff8da43a7d08e00fe5f5fd25f0ead 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,7 @@
 CMAKE_MINIMUM_REQUIRED(VERSION 2.8.5)
 
+# NO_NINJA : Geant4 build fails with Ninja
+
 find_package(GaudiProject)
 gaudi_project(Geant4 v96r4p3
               DATA Geant4Files VERSION v96r*)