diff --git a/projectbuilders/CMakeLists.txt b/projectbuilders/CMakeLists.txt
index 80d7866..825ca8b 100644
--- a/projectbuilders/CMakeLists.txt
+++ b/projectbuilders/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_subdirectory(makebuilder)
-add_subdirectory(ninjabuilder)
+ecm_optional_add_subdirectory(ninjabuilder)
 ecm_optional_add_subdirectory(cmakebuilder)
 if (KDevelop-PG-Qt_FOUND)
     ecm_optional_add_subdirectory(qmakebuilder)