diff --git a/doc/docker/fpm/Dockerfile b/doc/docker/fpm/Dockerfile
index 8dd98ecceb..dc6f39b65d 100644
--- a/doc/docker/fpm/Dockerfile
+++ b/doc/docker/fpm/Dockerfile
@@ -17,7 +17,8 @@ RUN apt-get update \
 	&& apt-get install -y software-properties-common \
 	&& LC_ALL=C.UTF-8 add-apt-repository -y ppa:ondrej/php \
 	&& apt-get update \
-	&& bash -c "apt-get install -y php$PHP_VERSION-{cli,mysql,json,gd,xsl,bz2,opcache,apcu,tidy,zip,bcmath,mbstring,smbclient,ldap,curl,fpm,pgsql,gmp,memcached}" \
+	&& bash -c "apt-get install -y php$PHP_VERSION-{cli,mysql,gd,xsl,bz2,opcache,apcu,tidy,zip,bcmath,mbstring,smbclient,ldap,curl,fpm,pgsql,gmp,memcached}" \
+	&& bash -c "[[ $PHP_VERSION =~ ^8\..* ]] || apt-get install -y php$PHP_VERSION-json" \
 	# fpm and php.ini settings
 	&& sed -e 's/^;\?listen \?=.*/listen = 9000/g' \
 		-e '/allowed_clients/d' \
@@ -68,9 +69,10 @@ fi; \
 rm composer-setup.php; \
 exit $RESULT' \
 	# build EGroupware
-	&& cd /usr/share \
 	&& composer.phar self-update 1.8.6 \
-	&& composer.phar create-project --prefer-dist --no-scripts --no-dev egroupware/egroupware:$VERSION \
+	&& cd /usr/share \
+	&& [ $PHP_VERSION = "8.0" ] && COMPOSER_EXTRA=--ignore-platform-reqs || true \
+	&& composer.phar create-project $COMPOSER_EXTRA --prefer-dist --no-scripts --no-dev egroupware/egroupware:$VERSION \
 	&& cd egroupware \
 	&& npm install \
 	&& grunt \
diff --git a/doc/docker/fpm/build.sh b/doc/docker/fpm/build.sh
index 0a2de26f4c..7e8228c289 100755
--- a/doc/docker/fpm/build.sh
+++ b/doc/docker/fpm/build.sh
@@ -1,4 +1,5 @@
 #!/bin/bash -x
+# To build PHP 8 snapshots out of master: doc/docker/fpm/build.sh 8.0 21.1.<date> master
 
 cd $(dirname $0)
 
@@ -13,18 +14,19 @@ fi
 
 DEFAULT=$(git branch|grep ^*|cut -c3-)
 TAG=${1:-$DEFAULT}
-VERSION=$TAG
+VERSION=${2:-$TAG}
 BRANCH=$(echo $VERSION|sed 's/\.[0-9]\{8\}$//')
-[ $VERSION = $BRANCH ] && VERSION="$BRANCH.x-dev"
+[ $VERSION = $BRANCH ] && VERSION="dev-$BRANCH"
 
-[ $VERSION = "$DEFAULT.x-dev" ] && {
-	grep self.version composer.json | while read pack version; do composer update $(echo $pack|cut -d'"' -f2); done
+[ $VERSION = "dev-$DEFAULT" ] && (
+  cd ../../..
+	composer update 'egroupware/*'
 	git status composer.lock|grep composer.lock && {
 		git stash; git pull --rebase; git stash pop
 		git commit -m 'updating composer.lock with latest commit hashed for egroupware/* packages' composer.lock
 		VERSION="$VERSION#$(git push|grep $DEFAULT|cut -c4-10)"
 	}
-}
+)
 
 # add PHP_VERSION to TAG, if not the default PHP version
 [ $PHP_VERSION != $DEFAULT_PHP_VERSION ] && TAG=$TAG-$PHP_VERSION
@@ -39,7 +41,7 @@ docker build --no-cache --build-arg "VERSION=$VERSION" --build-arg "PHP_VERSION=
 	#	docker tag egroupware/egroupware:$TAG egroupware/egroupware:latest
 	#	docker push egroupware/egroupware:latest
 	#}
-	[ "$BRANCH" != $VERSION -a "${BRANCH}.x-dev" != $VERSION ] && {
+	[ "$BRANCH" != $VERSION -a "dev-${BRANCH}" != $VERSION ] && {
 		docker tag egroupware/egroupware:$TAG egroupware/egroupware:$BRANCH
 		docker push egroupware/egroupware:$BRANCH
 	}