diff --git a/docs/source/conf.py b/docs/source/conf.py
index a4df2c9..55c8a6d 100755
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -16,7 +16,11 @@
 # The suffix(es) of source filenames.
 # You can specify multiple suffix as a list of string:
 #
-source_suffix = ['.rst', '.md']
+source_suffix = {
+    '.rst': 'restructuredtext',
+    '.txt': 'markdown',
+    '.md': 'markdown',
+}
 # source_suffix = '.md'
 
 # The master toctree document.