How to properly modify a piece of template in Jade?

Question

Pug

There is template.jade

doctype html
html
  head
    meta(charset='utf-8')
    meta(http-equiv='X-UA-Compatible', content='IE=edge')
    block pageTitle
    title TEMPLATE | #{pageTitle}
    meta(name='description', content='')
    meta(name='viewport', content='width=device-width, initial-scale=1')
    link(rel='stylesheet', href='../css/main.css')
    //[if lt IE 9]><script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script><![endif]
  block body
    block bottom-script
      script(src='../js/plugins.js')
      script(src='../js/main.js')

There is a page template:

extend _template
block pageTitle
  - var pageTitle = 'Sample Page'
block prepend body
  body
    include parts/_header
    main.page-content.sample-page
      ... content ...

There is a header template _header.jade:

header.main-header
  ... content ...

The header on different pages can be of different heights: normal and narrow (determined by the presence of .slim for the header)
Question: how can I include _header.jade with the .slim class on certain pages? Or how should the structure be redone if it is wrong from Jade's point of view?

Answer 1

just include another header
include parts/_header-slim on the necessary pages