diff --git a/docker/nginx.Dockerfile b/docker/nginx.Dockerfile
index edb7aed7..fe4687c3 100644
--- a/docker/nginx.Dockerfile
+++ b/docker/nginx.Dockerfile
@@ -3,6 +3,9 @@ FROM nginx:mainline-alpine
 # https://blog.packagecloud.io/eng/2017/02/21/set-environment-variable-save-thousands-of-system-calls/
 ENV TZ=:/etc/localtime
 
+# default PHP-FPM upstream
+ENV PHP_FPM=php-fpm
+
 # nginx settings
 COPY docker/nginx/nginx.conf /etc/nginx/nginx.conf
 COPY docker/nginx/default.conf /etc/nginx/conf.d/default.conf
diff --git a/docker/nginx/upstream.conf.template b/docker/nginx/upstream.conf.template
index 326af461..6e970538 100644
--- a/docker/nginx/upstream.conf.template
+++ b/docker/nginx/upstream.conf.template
@@ -1,3 +1,3 @@
 upstream php-fpm-upstream {
-  server ${PHP_FPM:-php-fpm}:9000;
+  server ${PHP_FPM}:9000;
 }