diff --git a/doc/requirements.txt b/doc/requirements.txt
index 66326ed96..bc82ae489 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,6 +1,6 @@
 alabaster==0.7.7
 argh==0.26.1
-Babel==2.2.0
+Babel==2.9.1
 backports-abc==0.4
 backports.ssl-match-hostname==3.5.0.1
 certifi==2016.2.28