diff --git a/Dockerfile b/Dockerfile
index 879cff1..6c58672 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,8 +1,9 @@
-ARG PORT=3000
-ENV PORT=$PORT
 # Use the official lightweight Node.js 12 image.
 # https://hub.docker.com/_/node
 FROM node:12-alpine
+
+ARG PORT=3000
+ENV PORT=$PORT
 # Create and change to the app directory.
 WORKDIR /usr/src/app
 # Copy application dependency manifests to the container image.