diff --git a/docs/requirements.txt b/docs/requirements.txt
index 08212ce..1febcf2 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -13,6 +13,6 @@ sphinxcontrib-htmlhelp==2.0.0
 sphinxcontrib-jsmath==1.0.1
 sphinxcontrib-qthelp==1.0.3
 sphinxcontrib-serializinghtml==1.1.5
-tornado==5.1.1
+tornado==6.5
 typing-extensions==4.1.1
 sphinx-book-theme==1.0.0