niska on "[Plugin: W3 Total Cache] post-sitemap.xml and other sitemap files doesn't get cached"

I updated to w3 total cache 0.9.2.6 and now I'm unable to get caching of xml files to work. Checking the footer of post-sitemap.xml (generated by the yoast seo plugin) say:

<!-- Performance optimized by W3 Total Cache. Learn more: http://www.w3-edge.com/wordpress-plugins/

Minified using disk: basic
Page Caching using disk: enhanced

 Served from: www.domain.com @ 2013-02-05 10:25:30 by W3 Total Cache -->

But when reloading the page (I'm not logged in) I get a new timestamp.

What could be wrong?

http://wordpress.org/extend/plugins/w3-total-cache/