Empty page-sitemap.xml in the Sitemap

WordPress version: 3.5
WordPress SEO version: 1.3.4.1

I did this: Configured sitemaps within the plugin to include pages.

I expected the plugin to do this: The sitemap_index.xml to contain a valid page-sitemap.xml including all my pages.

Instead it did this: the page-sitemap.xml is empty

http://wordpress.org/extend/plugins/wordpress-seo/