diff --git a/.buildkite/scripts/test_old_deps.sh b/.buildkite/scripts/test_old_deps.sh
index cdb77b556c..9905c4bc4f 100755
--- a/.buildkite/scripts/test_old_deps.sh
+++ b/.buildkite/scripts/test_old_deps.sh
@@ -6,7 +6,7 @@
 set -ex
 
 apt-get update
-apt-get install -y python3.5 python3.5-dev python3-pip libxml2-dev libxslt-dev zlib1g-dev tox
+apt-get install -y python3.5 python3.5-dev python3-pip libxml2-dev libxslt-dev xmlsec1 zlib1g-dev tox
 
 export LANG="C.UTF-8"