diff --git a/docs/notebook_requirements.txt b/docs/notebook_requirements.txt
index 8afe0f87..ca69d159 100644
--- a/docs/notebook_requirements.txt
+++ b/docs/notebook_requirements.txt
@@ -48,7 +48,7 @@ soupsieve==2.3.2.post1
 terminado==0.8.3
 testpath==0.3.1
 tinycss2==1.1.1
-tornado==6.3.3
+tornado==6.4.2
 traitlets==5.0.0
 wcwidth==0.1.7
 webencodings==0.5.1