Edit page slug from admin

[UPDATE] I finally found the solution: simply change the key to header.slug.
Don't know why the field behave the way it did without that though.

I'm trying to allow editors to edit the slug for a page (multi-language site).

I've set up my blueprint like so:

form:
  fields:
    tabs:
      type: tabs
      active: 1

      fields:
        content:
          type: tab
          title: Content

          fields: 
            slug:
              type: text
              label: Slug

Event though the slug itself shows up in the field when the form loads, it's impossible to change it. I can edit the field no problem, and I'm not getting errors, the page simply saves and restores the field content to its original value.
Is there a way to achieve this?