diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index 33cf92ac1e..2768884c20 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,7 +1,7 @@
-add_subdirectory(desktop)
-add_subdirectory(kwincompositing)
-add_subdirectory(kwindecoration)
-add_subdirectory(kwinscreenedges)
-add_subdirectory(kwintabbox)
-add_subdirectory(windowbehaviour)
-add_subdirectory(windowspecific)
+ecm_optional_add_subdirectory(desktop)
+ecm_optional_add_subdirectory(kwincompositing)
+ecm_optional_add_subdirectory(kwindecoration)
+ecm_optional_add_subdirectory(kwinscreenedges)
+ecm_optional_add_subdirectory(kwintabbox)
+ecm_optional_add_subdirectory(windowbehaviour)
+ecm_optional_add_subdirectory(windowspecific)