Ser expires in nginx?

[Azurel]

Hello. I have set nginx for "Smart static files processing" and "Serve static files directly by nginx". Not I want set a expires header for images, css and javascript files. For this I added:

location ~* \.(gif|png|jpeg|jpg|css|js)$ {
expires 2592000s;
}

The Response Headers for a image said:
http://cdn.example.com/images/folder/image.png

Accept-Ranges:bytes
Connection:keep-alive
Content-Length:4290
Content-Type:image/png
Date:Mon, 08 Feb 2016 17:35:25 GMT
ETag:"568acf11-10c2"
Last-Modified:Mon, 04 Jan 2016 19:59:13 GMT
Server:nginx

Is expires here not working?