diff --git a/t/Dockerfile b/t/Dockerfile
index 38a84ee4..2dd70c46 100644
--- a/t/Dockerfile
+++ b/t/Dockerfile
@@ -1,11 +1,17 @@
-# DOCKER_NAME=kamailio-config-tests-jessie
-FROM docker.mgm.sipwise.com/sipwise-jessie:latest
+# DOCKER_NAME=kamailio-config-tests-stretch
+FROM docker.mgm.sipwise.com/sipwise-stretch:latest
 
 # Important! Update this no-op ENV variable when this Dockerfile
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2016-11-04
+ENV REFRESHED_AT 2017-09-20
+
+# test execution; we need the backport of python3-junitxml from our own
+# repository since it's not part of Debian/stretch
+# files that get-code generates
+COPY t/sources.list.d/builddeps.list /etc/apt/sources.list.d/
+COPY t/sources.list.d/preferences /etc/apt/preferences.d/
 
 RUN apt-get update
 RUN apt-get install --assume-yes python-yaml python-junitxml \
@@ -18,13 +24,20 @@ WORKDIR /code/
 ################################################################################
 # Instructions for usage
 # ----------------------
-# When you want to build the base image from scratch (jump to the next section if you don't want to build yourself!):
-# % docker build --tag="kamailio-config-tests-jessie" .
-# % docker run --rm -i -t -v $(pwd)/..:/code:rw kamailio-config-tests-jessie:latest bash
+# When you want to build the base image from scratch
+# (jump to the next section if you don't want to build yourself!):
+#
+# you need to put the proper NGCP sources at t/sources.list.d/builddeps.list
+# for instance, trunk:
+# echo "deb https://deb.sipwise.com/autobuild/ release-trunk-stretch main" > /
+#  t/sources.list.d/builddeps.list
+#
+# % docker build --tag="kamailio-config-tests-stretch" .
+# % docker run --rm -i -t -v $(pwd)/..:/code:rw kamailio-config-tests-stretch:latest bash
 #
 # Use the existing docker image:
-# % docker pull docker.mgm.sipwise.com/kamailio-config-tests-jessie
-# % docker run --rm -i -t -v $(pwd)/:/code:rw docker.mgm.sipwise.com/kamailio-config-tests-jessie:latest bash
+# % docker pull docker.mgm.sipwise.com/kamailio-config-tests-stretch
+# % docker run --rm -i -t -v $(pwd)/:/code:rw docker.mgm.sipwise.com/kamailio-config-tests-stretch:latest bash
 #
 # Inside docker (the command is in history, just press UP button):
 #   ./t/testrunner
diff --git a/t/sources.list.d/builddeps.list b/t/sources.list.d/builddeps.list
new file mode 100644
index 00000000..e69de29b
diff --git a/t/sources.list.d/preferences b/t/sources.list.d/preferences
new file mode 100644
index 00000000..e69de29b