diff --git a/docs/conf.py b/docs/conf.py
index <HASH>..<HASH> 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -2,6 +2,7 @@
 #
 # This file is part of Invenio.
 # Copyright (C) 2015-2018 CERN.
+# Copyright (C) 2022 Graz University of Technology.
 #
 # Invenio is free software; you can redistribute it and/or modify it
 # under the terms of the MIT License; see LICENSE file for more details.
@@ -68,7 +69,7 @@ release = __version__
 #
 # 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"
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
fix docs compatibilty problem with Sphinx>=<I>