diff --git a/requirements.txt b/requirements.txt
index 8bd1509..50589d3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -49,7 +49,7 @@ isort==4.3.21
 jdcal==1.4
 Jinja2==2.10.1
 kiwisolver==1.0.1
-lxml==4.5.0
+lxml==4.9.1
 madrigalWeb==3.1.12
 MarkupSafe==1.1.1
 matplotlib==2.2.2