diff --git a/conf.py b/conf.py
index 4c4ca270826..2334df8d18f 100644
--- a/conf.py
+++ b/conf.py
@@ -63,7 +63,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.