diff --git a/doc/conf.py b/doc/conf.py
index 4a6f8f580..4bb4f4c51 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -7,7 +7,8 @@ import sphinx
 
 
 extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.todo',
-              'sphinx.ext.autosummary', 'sphinx.ext.extlinks']
+              'sphinx.ext.autosummary', 'sphinx.ext.extlinks',
+              'sphinx.ext.viewcode']
 
 master_doc = 'contents'
 templates_path = ['_templates']