diff --git a/Dockerfile b/Dockerfile
index 9c9920e..f0207de 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,7 @@
 FROM caddy:builder-alpine as caddy 
 RUN xcaddy build --with github.com/baldinof/caddy-supervisor@v0.6.0
 ARG PHP_VERSION=7.4
-FROM php:${PHP_VERSION}-fpm-alpine
+FROM php:$PHP_VERSION-fpm-alpine
 COPY --from=caddy /usr/bin/caddy /usr/bin
 COPY Caddyfile /usr/local/etc/caddy/Caddyfile
 COPY php.ini /usr/local/etc/php/conf.d