diff --git a/docker/webapp/Dockerfile b/docker/webapp/Dockerfile
index 5d375dc4..a26ae8c6 100755
--- a/docker/webapp/Dockerfile
+++ b/docker/webapp/Dockerfile
@@ -1,26 +1,28 @@
 FROM apheleia/swoole:latest
 
 USER root
 
 RUN dnf -y install findutils gnupg2 git rsync && \
     dnf clean all
 
 EXPOSE 8000
 
 ARG GIT_REF=master
 ARG GIT_REMOTE=https://git.kolab.org/source/kolab.git
 ARG CONFIG=config.prod
+ARG OVERLAY_GIT_REMOTE
+ARG OVERLAY_GIT_REF=master
 #Set this to prod or dev
 ARG RELEASE_MODE=prod
 COPY build.sh /build.sh
 RUN /build.sh && \
     chgrp -R 0 /opt/app-root /tmp && \
     chmod -R g=u /opt/app-root /tmp && \
     chown -R 1001:0 /opt/app-root /tmp
 
 COPY init.sh /init.sh
 COPY update.sh /update.sh
 
 USER 1001
 
 CMD [ "/init.sh" ]
diff --git a/docker/webapp/build.sh b/docker/webapp/build.sh
index 25736f7f..239bf8c1 100755
--- a/docker/webapp/build.sh
+++ b/docker/webapp/build.sh
@@ -1,46 +1,51 @@
 #!/bin/bash
 set -e
 set -x
 
 echo -e "Building with the following ulimit: limit: $(ulimit -n)\n"
 echo -e "If you run into EMFILE errors, this is the reason"
 
 mkdir /src
 cd /src
 
 function checkout() {
     if [ ! -d "$1" ]; then
         git clone "$2" "$1"
         pushd "$1"
         git checkout "$3" 
         popd
     fi
 }
 
 checkout kolab $GIT_REMOTE $GIT_REF
 
-pushd kolab
-#TODO support injecting a custom overlay into the build process here
-bin/configure.sh $CONFIG
-# In the docker-compose case we copy the .env file during the init phase, otherwise we use the environment for configuration.
-rm src/.env
-popd
+# We either apply a remote overlay, or one of the built in deployment configs.
+if [[ -z $OVERLAY_GIT_REMOTE ]]; then
+    pushd kolab
+    bin/configure.sh $CONFIG
+    # In the docker-compose case we copy the .env file during the init phase, otherwise we use the environment for configuration.
+    rm src/.env
+    popd
+else
+    checkout overlay $OVERLAY_GIT_REMOTE $OVERLAY_GIT_REF
+    rsync -av overlay/src/ kolab/src/
+fi
 
 rm -rf /opt/app-root/src
 cp -a kolab/src /opt/app-root/src
 cd /opt/app-root/src/
 
 mkdir -p storage/framework/{sessions,views,cache}
 mkdir -p database/seeds
 
 php -dmemory_limit=-1 $(command -v composer) install
 npm -g install npm
 /usr/local/bin/npm install
 ./artisan storage:link
 ./artisan clear-compiled
 ./artisan horizon:install
 if [ ! -f 'resources/countries.php' ]; then
     ./artisan data:countries
 fi
 
 /usr/local/bin/npm run $RELEASE_MODE