diff --git a/requirements/documentation.txt b/requirements/documentation.txt
index 0e59402..8097030 100644
--- a/requirements/documentation.txt
+++ b/requirements/documentation.txt
@@ -7,4 +7,4 @@ Markdown==2.6.11
 MarkupSafe==1.0
 mkdocs==0.17.3
 PyYAML==3.12
-tornado==5.0
+tornado==6.4.2