diff --git a/requirements_ci.txt b/requirements_ci.txt
index 49a4050..f0a1b1b 100644
--- a/requirements_ci.txt
+++ b/requirements_ci.txt
@@ -45,7 +45,7 @@ jupyter-client==6.1.7
 jupyter-core==4.7.0
 jupyterlab-pygments==0.1.2
 lazy-object-proxy==1.4.3
-lxml==4.6.2
+lxml==4.9.1
 m2r2==0.2.7
 MarkupSafe==1.1.1
 mccabe==0.6.1