Wordpress MailingEventSubscribe URL uses wp-admin/admin.php

I'm setting up a mailing list in CiviCRM (originally 4.7.14, now 4.7.16) and the latest Wordpress. I created a plugin to call MailingEventSubscribe to add an email to a group, pending clicking the link in a confirmation email.

In Administer->System Settings->CMS Database Integration, I have the base page set to /civicrm. Yet when the mailing list subscribe confirmation is sent, the subscribe.url token uses http://mydomain.com/wp-admin/admin.php?page=CiviCRM&q=civicrm/mailing/confirm&reset=1&etc...

I tracked this down to /CRM/Utils/System/Wordpress.php line 280. The condition is met of is_admin() and !$frontend, so the $base is set to wp-admin/admin.php instead of using the /civicrm/ base.

I can fix this by changing line 246 of CRM/Mailing/Event/BAO/Subscribe.php to set $frontend to 1:

$url = CRM_Utils_System::url('civicrm/mailing/confirm',
"reset=1&cid={$this->contact_id}&sid={$this->id}&h={$this->hash}",
TRUE, '', '', 1
);

But I don't know whether this will cause other problems.

I suspect this will also need to be done where the unsubscribe.url is generated, and maybe elsewhere.

I'm not sure of the cleanest way to address this problem for all cases.