diff --git a/requirements-doc.txt b/requirements-doc.txt
index 9856d5f..54d3465 100644
--- a/requirements-doc.txt
+++ b/requirements-doc.txt
@@ -1,7 +1,7 @@
 alabaster==0.7.10
 asn1crypto==0.23.0
 attrs==17.3.0
-Babel==2.5.1
+Babel==2.9.1
 certifi==2017.11.5
 cffi==1.11.2
 chardet==3.0.4