diff --git a/Dockerfile b/Dockerfile
index 0ae4d52..4c41130 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,7 +6,7 @@ LABEL maintainer="Robert Kaussow <mail@geeklabor.de>" \
     org.label-schema.vendor="Robert Kaussow" \
     org.label-schema.schema-version="1.0"
 
-ARG FRESHRSS_VERSION=master
+ARG FRESHRSS_VERSION="${FRESHRSS_VERSION:-master}"
 ARG FRESHRSS_TARBALL=https://github.com/FreshRSS/FreshRSS/archive/${FRESHRSS_VERSION}.tar.gz
 
 RUN apk --update add --virtual .build-deps tar curl && \
@@ -18,7 +18,7 @@ RUN apk --update add --virtual .build-deps tar curl && \
     rm -f /etc/php7/php-fpm.d/www.conf && \
     mkdir -p /var/www/app && \
     mkdir /var/www/.postgresql && \
-    echo "Installing FreshRSS '$FRESHRSS_VERSION' ..." && \
+    echo "Installing FreshRSS '${FRESHRSS_VERSION}' ..." && \
     curl -SsL ${FRESHRSS_TARBALL} | tar xz -C /var/www/app/ --strip-components=1 && \
     curl -SsL -o /etc/php7/browscap.ini https://browscap.org/stream?q=Lite_PHP_BrowsCapINI && \
     apk del .build-deps && \