diff --git a/concourse_unit_test_task b/concourse_unit_test_task
index b3a022b684..0dcf32d7d5 100644
--- a/concourse_unit_test_task
+++ b/concourse_unit_test_task
@@ -2,7 +2,7 @@ export DEBIAN_FRONTEND=noninteractive && \
 export UPPER_CONSTRAINTS_FILE=https://raw.githubusercontent.com/sapcc/requirements/stable/stein-m3/upper-constraints.txt && \
 apt-get update && \
 apt-get install -y build-essential python-pip python-dev python3-dev git libpcre++-dev gettext && \
-pip install tox && \
+pip install tox "six>=1.14.0" && \
 git clone -b stable/stein-m3 --single-branch https://github.com/sapcc/manila.git --depth=1 && \
 cd manila && \
 tox -e py27