diff --git a/build.sh b/build.sh
index f92d66e..1d37d54 100755
--- a/build.sh
+++ b/build.sh
@@ -10,7 +10,7 @@ if [ "$1" = "dev" ]; then
 fi
 
 REG_URL=${REGISTRY}_URL
-TAG=0.1
+: "${TAG:=0.1}"
 
 if [ "$EVENT_TYPE" = "cron" ]  || [ "$DEV" = "true" ]; then
     python3 -m venv venv
diff --git a/core/Dockerfile b/core/Dockerfile
index da0d1e0..acd4057 100644
--- a/core/Dockerfile
+++ b/core/Dockerfile
@@ -7,7 +7,7 @@ COPY docker-entrypoint.sh /usr/local/bin/
 
 #Install all required packages, add user for executing mailman and set execution rights for startup script
 RUN apk update \
-    && apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev \
+    && apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev libffi-dev \
     && apk add bash su-exec postgresql-client mysql-client curl \
     && pip install psycopg2 \
                    mailman==3.1.1 \
diff --git a/core/Dockerfile.dev b/core/Dockerfile.dev
index 66589c3..08045bc 100644
--- a/core/Dockerfile.dev
+++ b/core/Dockerfile.dev
@@ -13,7 +13,7 @@ ARG MM3_HK_REF
 #Install all required packages, add user for executing mailman and set execution
 #rights for startup script
 RUN apk update \
-    && apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev git \
+    && apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev git libffi-dev \
     && apk add bash su-exec postgresql-client mysql-client curl \
     && pip install -U psycopg2 pymysql \
                       git+https://gitlab.com/mailman/mailman@${CORE_REF} \
diff --git a/core/docker-entrypoint.sh b/core/docker-entrypoint.sh
index e6812ee..870a8ec 100755
--- a/core/docker-entrypoint.sh
+++ b/core/docker-entrypoint.sh
@@ -114,7 +114,7 @@ then
 fi
 
 # Generate a basic mailman.cfg.
-cat > /etc/mailman.cfg << EOF
+cat >> /etc/mailman.cfg << EOF
 [runner.retry]
 sleep_time: 10s