diff --git a/docs/conf.py b/docs/conf.py
index 63c576393138f033ead0caf1b97b1bd74afb1b8a..7581cb252c4017c01ed40a70fce9745952b7e422 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -49,6 +49,9 @@ source_suffix = {
     '.md': 'markdown',
 }
 
+# The master toctree document.
+master_doc = 'index'
+
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 # This pattern also affects html_static_path and html_extra_path.