diff --git a/Makefile b/Makefile
index 6841ff1..0b66483 100644
--- a/Makefile
+++ b/Makefile
@@ -5,56 +5,6 @@ TEST_PACKAGE_DEPS := build-essential python python-pip procps python-dev python-
 
 DOCKER_RUN_TEST := docker run -v $(PWD):/mnt:ro
 
-# test installation using Debian packages
-DOCKER_DEB_TEST := sh -euxc ' \
-	apt-get update \
-	&& apt-get install -y --no-install-recommends $(TEST_PACKAGE_DEPS) \
-	&& dpkg -i /mnt/dist/*.deb \
-	&& tmp=$$(mktemp -d) \
-	&& cp -r /mnt/* "$$tmp" \
-	&& cd "$$tmp" \
-	&& pip install --upgrade pip \
-	&& hash -r \
-	&& pip --version \
-	&& pip install --upgrade setuptools distribute \
-	&& pip install -r requirements-dev.txt \
-	&& py.test tests/ \
-	&& exec dumb-init /mnt/tests/test-zombies \
-'
-
-# test installation using `pip install`
-DOCKER_PYTHON_TEST := sh -uexc ' \
-	apt-get update \
-	&& apt-get install -y --no-install-recommends $(TEST_PACKAGE_DEPS) \
-	&& tmp=$$(mktemp -d) \
-	&& cp -r /mnt/* "$$tmp" \
-	&& cd "$$tmp" \
-	&& python setup.py clean \
-	&& python setup.py sdist \
-	&& pip install --upgrade pip \
-	&& hash -r \
-	&& pip install --upgrade setuptools distribute \
-	&& pip install -vv dist/*.tar.gz \
-	&& pip install -r requirements-dev.txt \
-	&& py.test tests/ \
-	&& exec dumb-init /mnt/tests/test-zombies \
-'
-
-# test several Python versions using tox
-DOCKER_TOX_TEST := sh -uexc ' \
-	apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0x5BB92C09DB82666C \
-	&& echo "deb http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu xenial main" >> /etc/apt/sources.list \
-	&& apt-get update \
-	&& apt-get install -y --no-install-recommends python2.6-dev python2.7-dev python3.4-dev python3.5-dev git $(TEST_PACKAGE_DEPS) \
-	&& echo "We cannot use the Ubuntu versions of tox or virtualenv:" \
-	&& echo "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754248" \
-	&& pip install tox virtualenv \
-	&& hash -r \
-	&& tmp=$$(mktemp -du) \
-	&& cp -r /mnt "$$tmp" \
-	&& cd "$$tmp" \
-	&& tox \
-'
 .PHONY: build
 build: VERSION.h
 	$(CC) $(CFLAGS) -o dumb-init dumb-init.c
@@ -124,13 +74,13 @@ itest_jessie: _itest-debian-jessie
 itest_stretch: _itest-debian-stretch
 
 itest_tox:
-	$(DOCKER_RUN_TEST) ubuntu:xenial $(DOCKER_TOX_TEST)
+	$(DOCKER_RUN_TEST) ubuntu:xenial /mnt/ci/docker-tox-test
 
 _itest-%: _itest_deb-% _itest_python-%
 	@true
 
 _itest_python-%:
-	$(DOCKER_RUN_TEST) $(shell sed 's/-/:/' <<< "$*") $(DOCKER_PYTHON_TEST)
+	$(DOCKER_RUN_TEST) $(shell sed 's/-/:/' <<< "$*") /mnt/ci/docker-python-test
 
 _itest_deb-%: builddeb-docker
-	$(DOCKER_RUN_TEST) $(shell sed 's/-/:/' <<< "$*") $(DOCKER_DEB_TEST)
+	$(DOCKER_RUN_TEST) $(shell sed 's/-/:/' <<< "$*") /mnt/ci/docker-deb-test
diff --git a/CI/circle b/ci/circle
similarity index 100%
rename from CI/circle
rename to ci/circle
diff --git a/ci/docker b/ci/docker
new file mode 100644
index 0000000..fb725e4
--- /dev/null
+++ b/ci/docker
@@ -0,0 +1,23 @@
+if grep -qE '\<lucid\>' /etc/apt/sources.list; then
+    # lucid was archived, breaking the base image
+    # https://github.com/docker-library/official-images/issues/1902
+    sed -i 's/archive\.ubuntu\.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
+fi
+
+apt-get update
+apt-get install -y --no-install-recommends \
+    build-essential \
+    procps \
+    python \
+    python-dev \
+    python-pip \
+    python-setuptools
+
+pip install --upgrade pip
+hash -r
+pip --version
+
+cp -r /mnt/ /test
+cd /test
+
+# vim: ft=sh
diff --git a/ci/docker-deb-test b/ci/docker-deb-test
new file mode 100755
index 0000000..2283e0a
--- /dev/null
+++ b/ci/docker-deb-test
@@ -0,0 +1,11 @@
+#!/bin/bash -eux
+set -o pipefail
+
+. /mnt/ci/docker
+
+dpkg -i dist/*.deb
+pip install --upgrade setuptools distribute
+pip install -r requirements-dev.txt
+py.test tests/
+
+exec dumb-init /mnt/tests/test-zombies
diff --git a/ci/docker-python-test b/ci/docker-python-test
new file mode 100755
index 0000000..d8c60de
--- /dev/null
+++ b/ci/docker-python-test
@@ -0,0 +1,13 @@
+#!/bin/bash -eux
+set -o pipefail
+
+. /mnt/ci/docker
+
+python setup.py clean
+python setup.py sdist
+pip install --upgrade setuptools distribute
+pip install -vv dist/*.tar.gz
+pip install -r requirements-dev.txt
+py.test tests/
+
+exec dumb-init /mnt/tests/test-zombies \
diff --git a/ci/docker-tox b/ci/docker-tox
new file mode 100644
index 0000000..9907bc8
--- /dev/null
+++ b/ci/docker-tox
@@ -0,0 +1,21 @@
+#!/bin/bash -eux
+set -o pipefail
+
+. /mnt/ci/docker
+
+apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0x5BB92C09DB82666C
+echo 'deb http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu xenial main' >> /etc/apt/sources.list
+apt-get update
+apt-get install -y --no-install-recommends \
+    git \
+    python2.6-dev \
+    python2.7-dev \
+    python3.4-dev \
+    python3.5-dev
+
+# We cannot use the Ubuntu versions of tox or virtualenv:
+# https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754248
+pip install tox virtualenv
+hash -r
+
+tox
diff --git a/ci/docker-tox-test b/ci/docker-tox-test
new file mode 100755
index 0000000..17b44f7
--- /dev/null
+++ b/ci/docker-tox-test
@@ -0,0 +1,4 @@
+#!/bin/bash -eux
+set -o pipefail
+
+. /mnt/ci/docker
diff --git a/circle.yml b/circle.yml
index da50d3c..0281c5c 100644
--- a/circle.yml
+++ b/circle.yml
@@ -14,5 +14,5 @@ dependencies:
 
 test:
     override:
-        - CI/circle:
+        - ci/circle:
             parallel: true
diff --git a/tox.ini b/tox.ini
index 56f6db7..d9d13ca 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,7 @@ envlist = py26,py27,py34,py35
 
 [testenv]
 deps = -r{toxinidir}/requirements-dev.txt
+passenv = HOME SSH_AUTH_SOCK USER
 commands =
     python -m pytest
     pre-commit run --all-files