diff --git a/Doc/conf.py b/Doc/conf.py
index b6d212d..5ed1140 100644
--- a/Doc/conf.py
+++ b/Doc/conf.py
@@ -13,8 +13,8 @@
 # General configuration
 # ---------------------
 
-extensions = ['sphinx.ext.refcounting', 'sphinx.ext.coverage',
-              'sphinx.ext.doctest', 'pyspecific']
+extensions = ['sphinx.ext.coverage', 'sphinx.ext.doctest',
+              'pyspecific', 'c_annotations']
 templates_path = ['tools/sphinxext']
 
 # General substitutions.