diff --git a/requirements.txt b/requirements.txt
index c22f6b7..b1a6d18 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -31,7 +31,7 @@ joblib==1.0.1; python_version >= '3.6'
 jsonschema==3.2.0
 kiwisolver==1.3.2; python_version >= '3.7'
 llvmlite==0.37.0; python_version < '3.10' and python_version >= '3.7'
-lxml==4.6.3; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'
+lxml==4.9.1; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'
 matplotlib==3.4.3; python_version >= '3.7'
 more-itertools==8.9.0; python_version >= '3.5'
 mpmath==1.2.1