diff --git a/2013-05/requirements-dev.txt b/2013-05/requirements-dev.txt
index 9ebcdcc..5429426 100644
--- a/2013-05/requirements-dev.txt
+++ b/2013-05/requirements-dev.txt
@@ -1,7 +1,7 @@
 -r requirements.txt
 nose==1.1.2
 mock==0.8.0
-lxml==2.3.3
+lxml==4.6.5
 Pygments==1.5
 Sphinx==1.1.3
 docutils==0.9.1