diff --git a/doc/conf.py.in b/doc/conf.py.in
index 29b0b801f45d3054ddc56cfb1113953091637afa..cde5afda03930cfadbf17534b44dda1fd0e6fafd 100644
--- a/doc/conf.py.in
+++ b/doc/conf.py.in
@@ -39,7 +39,6 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.coverage',
               'sphinx.ext.mathjax',
               'sphinx.ext.ifconfig',
-              'sphinx.ext.viewcode',
               'sphinx.ext.extlinks', 'cmake']
 
 # Check first line of docstring for signatures (autofunction)