diff --git a/docs/meson.build b/docs/meson.build
index a4d0cc08d2..a8f66f279d 100644
--- a/docs/meson.build
+++ b/docs/meson.build
@@ -175,7 +175,9 @@ foreach plugin_name: list_plugin_res.stdout().split(':')
         gst_smart_index: true,
         gst_c_sources: [
             join_paths(root_rel, 'sys/*/*.[ch]'),
+            join_paths(root_rel, 'sys/*/*.cpp'),
             join_paths(root_rel, 'ext/*/*.[ch]'),
+            join_paths(root_rel, 'ext/*/*.cpp'),
             join_paths(root_rel, 'gst/*/*.[ch]'),
         ],
         dependencies: [gst_dep, plugins],