Permissions for module not present in admin/user/permissions

I can see that hook_permission is implemented in the module, but if I browse to admin/user/permissions I don't see anything listed for "mailsystem module".
Not being able to assign the "Administer Mail System" permission is making it difficult to configure the module.

I can probably work around this be adding the permission manually in the DB, but this still strikes me as a potential problem.