diff --git a/tools/requirements.txt b/tools/requirements.txt
index 9bbee77..11f50b3 100644
--- a/tools/requirements.txt
+++ b/tools/requirements.txt
@@ -15,7 +15,7 @@ httplib2==0.12.1
 idna==2.8
 jdcal==1.4
 kiwisolver==1.0.1
-lxml==4.3.3
+lxml==4.9.1
 matplotlib==3.0.2
 numpy==1.16.1
 openpyxl==2.6.0