diff --git a/docs/source/conf.py b/docs/source/conf.py
index e00d3f4..bf6c0bd 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -35,6 +35,9 @@ html_theme = 'sphinx_rtd_theme'
 epub_show_urls = 'footnote'
 
 
+formats: all
+
+
 html_static_path = ['_static']
 
 # These paths are either relative to html_static_path