diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8df557a..5f52918 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,2 +1,3 @@
-add_subdirectory( KChart )
-add_subdirectory( KGantt )
+include(ECMOptionalAddSubdirectory)
+ecm_optional_add_subdirectory( KChart )
+ecm_optional_add_subdirectory( KGantt )