--- a/doc/conf.py	2020-09-08 21:30:18.000000000 +0800
+++ b/doc/conf.py	2021-01-02 19:05:35.582692558 +0800
@@ -275,6 +275,6 @@
 # Intersphinx options
 intersphinx_cache_limit = 10  # days to keep the cached inventories
 intersphinx_mapping = {
-    'sphinx': ('http://www.sphinx-doc.org/en/latest/', None),
+    'sphinx': ('http://www.sphinx-doc.org/en/master/', None),
     'python': ('https://docs.python.org/3.6', None),
 }