diff --git a/docs/source/conf.py b/docs/source/conf.py
index c4e568bc..981075a1 100755
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -60,7 +60,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = En
+language = 'en'
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.