How to access Page Title in Email Notification in Form builder?

I am building a form, and I want to include the page title of the page where the form was submitted in the subject line of the email notification.

I am able to reference form fields in the subject line of of the Email Notification (%Name% works fine), however, I am having trouble adding the page title to the subject line as well. Here's what I am using at the moment:

"Message from {%Name%} about {%page.DocumentPageTitle%}"

Thanks,

Gabriel