diff --git a/requirements.txt b/requirements.txt
index 9fffbebdde..09f61e4643 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -39,7 +39,7 @@ isodate==0.5.4
 jsonschema==2.5.1
 jupyter-client==4.1.1
 jupyter-core==4.0.6
-lxml==3.5.0
+lxml==4.9.1
 mistune==0.7.1
 nbconvert==6.5.1
 nbformat==4.0.1