diff --git a/Dockerfile b/Dockerfile
index 3a5e789..2d557b6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -34,7 +34,7 @@ COPY . .
 CMD npm i
 
 # Expose the port that the application listens on.
-EXPOSE 3000
+EXPOSE ${APP_PORT}
 
 # Run the application.
 CMD node index.js