diff --git a/docs/conf.py b/docs/conf.py
index 41947d9f8..371632a56 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -36,7 +36,7 @@ master_doc = 'index'
 #
 # 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.