diff --git a/requirements.txt b/requirements.txt
index b317cdc..a479a18 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -38,7 +38,7 @@ jdcal==1.4.1
 joblib==0.14.1
 kiwisolver==1.1.0
 lazy-object-proxy==1.4.3
-lxml==4.4.1
+lxml==4.9.1
 matplotlib==3.1.1
 mccabe==0.6.1
 more-itertools==7.2.0