diff --git a/doc/manual/conf.py b/doc/manual/conf.py
index aa45391b5..dab2d6d6e 100644
--- a/doc/manual/conf.py
+++ b/doc/manual/conf.py
@@ -59,6 +59,7 @@ extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.mathjax',
     'sphinx.ext.viewcode',
+    'sphinx.ext.napoleon',
     'sphinxarg.ext',
     'sphinxcontrib.wavedrom',  # see also below for config
 ]