diff --git a/.github/workflows/docker-ci.yaml b/.github/workflows/docker-ci.yaml
index e81f1dd..e1d202e 100644
--- a/.github/workflows/docker-ci.yaml
+++ b/.github/workflows/docker-ci.yaml
@@ -119,8 +119,9 @@ jobs:
           TAGS="${IMAGE}:sha-${RELAY_SHA_SHORT}"
           if [ "$EVENT_NAME" = "push" ] || \
              [ "$EVENT_NAME" = "pull_request" ]; then
-            # Docker-repo push/PR: add docker branch tag
-            TAGS="${TAGS}"$'\n'"${IMAGE}:${REF_NAME}"
+            # Docker-repo push/PR: add docker branch tag (sanitize slashes)
+            BRANCH_TAG=$(echo "${REF_NAME}" | sed 's|/|-|g')
+            TAGS="${TAGS}"$'\n'"${IMAGE}:${BRANCH_TAG}"
           else
             # Dispatch: tags based on relay ref
             BRANCH_TAG=$(echo "${RELAY_REF}" | sed 's|/|-|g')
@@ -206,7 +207,6 @@ jobs:
     name: Integration test
     needs: build
     permissions: {}
-    if: github.event_name != 'pull_request'
     # TODO: revert to @main once cmlxc docker support is merged
     uses: chatmail/cmlxc/.github/workflows/lxc-test.yml@j4n/docker-support
     with:
diff --git a/README.md b/README.md
index 532274a..3ca5ffc 100644
--- a/README.md
+++ b/README.md
@@ -271,13 +271,13 @@ If you have an existing bare-metal chatmail installation and want to switch to D
 
 ## Development / Contributing
 
-To develop or contribute to the Docker setup:
-
-Clone the relay repo and add this repository as a submodule:
+Clone the relay repo and add this repository inside, then copy the `.dockerignore` and build:
 
 ```bash
 git clone https://github.com/chatmail/relay
 cd relay
 git clone https://github.com/chatmail/docker
 cd docker
+cp .dockerignore ..
+docker compose build
 ```
diff --git a/chatmail_relay.dockerfile b/chatmail_relay.dockerfile
index 33640fd..8b6b480 100644
--- a/chatmail_relay.dockerfile
+++ b/chatmail_relay.dockerfile
@@ -1,5 +1,37 @@
 # syntax=docker/dockerfile:1
-FROM jrei/systemd-debian:12 AS base
+
+# Build systemd-debian:12 base image locally
+# Vendoring https://github.com/j8r/dockerfiles/blob/master/systemd/debian/Dockerfile thats behind 
+# https://hub.docker.com/r/jrei/systemd-debian/tags?name=bookworm
+FROM debian:12 AS systemd-base
+
+ARG VERSION=12
+
+ENV LC_ALL=C
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update \
+    && apt-get install -y systemd systemd-sysv \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+RUN cd /lib/systemd/system/sysinit.target.wants/ \
+    && rm $(ls | grep -v systemd-tmpfiles-setup)
+
+RUN rm -f /lib/systemd/system/multi-user.target.wants/* \
+    /etc/systemd/system/*.wants/* \
+    /lib/systemd/system/local-fs.target.wants/* \
+    /lib/systemd/system/sockets.target.wants/*udev* \
+    /lib/systemd/system/sockets.target.wants/*initctl* \
+    /lib/systemd/system/basic.target.wants/* \
+    /lib/systemd/system/anaconda.target.wants/* \
+    /lib/systemd/system/plymouth* \
+    /lib/systemd/system/systemd-update-utmp*
+
+VOLUME [ "/sys/fs/cgroup" ]
+
+# Main chatmail-relay image
+FROM systemd-base AS base
 
 ENV LANG=en_US.UTF-8