diff --git a/TreeViz/requirements.txt b/TreeViz/requirements.txt
index e82c1c7..2338d28 100644
--- a/TreeViz/requirements.txt
+++ b/TreeViz/requirements.txt
@@ -49,7 +49,7 @@ joblib==0.7.1
 jsonschema==2.5.1
 jupyter-client==4.0.0
 jupyter-core==4.0.4
-lxml==3.3.3
+lxml==4.9.1
 matplotlib==1.3.1
 mistune==0.7.1
 mock==1.3.0