diff --git a/doc/source/conf.py b/doc/source/conf.py
index 7369758835..8036067c8e 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -46,6 +46,7 @@ sys.path.insert(0, os.path.abspath('./'))
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = ['sphinx.ext.autodoc',
+              'sphinx.ext.todo',
               'sphinx.ext.coverage',
               'sphinx.ext.viewcode',
               'oslo_config.sphinxconfiggen',