diff --git a/conf.py b/conf.py
index 77d0a221610efc8aabe50c85b50ef17966aa3f4a..6c286f5a510cbd503abe8aaa15d4421c7c44eea8 100644
--- a/conf.py
+++ b/conf.py
@@ -106,6 +106,9 @@ exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
 #
 # show_authors = False
 
+# Don't highlight text by default.
+highlight_language = 'none'
+
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'