diff --git a/Dockerfile b/Dockerfile
index 514c221e..a0f35f8c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,4 +10,4 @@ COPY . .
 ENV PORT=${PORT:-3000}
 USER 1000:1000
 
-CMD ./node_modules/probot/bin/probot.js run --port $PORT ./index.js
+CMD ["./node_modules/probot/bin/probot.js", "run", "--port", "$PORT", "./index.js"]