diff --git a/doc/reference/clapper-gtk/meson.build b/doc/reference/clapper-gtk/meson.build
index 24590ace..2562161f 100644
--- a/doc/reference/clapper-gtk/meson.build
+++ b/doc/reference/clapper-gtk/meson.build
@@ -16,6 +16,7 @@ custom_target('clapper-gtk-doc',
     gi_docgen,
     'generate',
     gi_docgen_common_args,
+    '--add-include-path=@0@'.format(join_paths(meson.project_build_root(), 'src', 'lib', 'clapper')),
     '--add-include-path=@0@'.format(join_paths(meson.project_build_root(), 'src', 'lib', 'clapper-gtk')),
     '--config=@INPUT0@',
     '--output-dir=@OUTPUT@',