diff --git a/docs/reference/gdk/meson.build b/docs/reference/gdk/meson.build
index f9150a9909..3f462f2f02 100644
--- a/docs/reference/gdk/meson.build
+++ b/docs/reference/gdk/meson.build
@@ -87,6 +87,8 @@ gnome.gtkdoc('gdk4',
              main_xml: 'gdk4-docs.xml',
              src_dir: [
 	       join_paths(meson.source_root(), 'gdk'),
+	       join_paths(meson.source_root(), 'gdk', 'x11'),
+	       join_paths(meson.source_root(), 'gdk', 'wayland'),
 	       join_paths(meson.build_root(), 'gdk'),
 	     ],
              dependencies: libgtk_dep,