diff --git a/requirements.txt b/requirements.txt
index e4b14b8..3cdca8b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -56,7 +56,7 @@ lazr.restfulclient==0.13.4
 lazr.uri==1.0.3
 lazy-object-proxy==1.3.1
 lockfile==0.12.2
-lxml==3.7.3
+lxml==4.9.1
 Markdown==2.6.8
 MarkupSafe==1.0
 matplotlib==2.0.2