diff --git a/docs/conf.py b/docs/conf.py
index a7366ffaba2..b32f68b7d84 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -122,8 +122,8 @@ def noop_decorator(*args, **kwargs):
 # source_suffix = ['.rst', '.md']
 source_suffix = ".rst"
 
-# The main toctree document.
-main_doc = "index"
+# The master toctree document.
+master_doc = "index"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.