add pre button to wp_editor manually

Hi, a plugin I use (AnsPress) calls wp_editor directly, and there I cannot see the pre button. Is there any way to modify the source code of AnsPress so that the pre button would also appear? I tried specifying custom tinymce options and providing a list for required buttons, but adding preformatted there did not have any effect on WP 3.9

Thanks,
Gergely

https://www.ads-software.com/plugins/tinymce-preformatted/