define('FORCE_SSL_LOGIN', true); define('FORCE_SSL_ADMIN', true);
in wp-config.php file.
When I edit a CPT, I get the following errors in my browser console
/wp-admin/post.php?post=xxxx&action=edit was loaded over HTTPS, but ran insecure content from http://xxxx/wp-content/plugins/cpt-onomies/js/admin-post.js?ver=3.8.1 and '/wp-admin/post.php?post=xxxx&action=edit' was loaded over HTTPS, but ran insecure content from 'http://xxxx/wp-content/plugins/cpt-onomies/css/admin-post.css?ver=3.8.1' files should also be loaded via https.
Without those 2 files, my CPT edit page is broken. Any ideas?