diff --git a/docs/source/conf.py b/docs/source/conf.py
index 04c6d6a2..84ce6584 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -50,7 +50,7 @@
 # You can specify multiple suffix as a list of string:
 #
 # source_suffix = ['.rst', '.md']
-source_suffix = '.rst'
+source_suffix = {'.rst': 'restructuredtext'}
 
 # The master toctree document.
 master_doc = 'index'