--- a/CMakeLists.txt	2015-10-02 22:36:55.186480671 +0200
+++ b/CMakeLists.txt	2015-10-02 22:38:40.048169719 +0200
@@ -17,6 +17,7 @@
 include(ECMSetupVersion)
 include(ECMInstallIcons)
 include(ECMMarkAsTest)
+include(ECMOptionalAddSubdirectory)
 include(GenerateExportHeader)
 include(FeatureSummary)
 include(KDEInstallDirs)
@@ -62,7 +63,7 @@
 install(FILES kde-gtk-config.desktop DESTINATION ${SERVICES_INSTALL_DIR})
 
 add_subdirectory(gtkproxies)
-add_subdirectory(gtk3proxies)
+ecm_optional_add_subdirectory(gtk3proxies)
 add_subdirectory(icons)
 add_subdirectory(tests)