Jade includes and blocks

I have many template pages (index.jade, catalog.jade, contacts.jade and so on), where I include some extra pieces of code (like header_piece.jade and footer_piece.jade) by include.

What I'm trying to do - I want to include something to the code, which is included by include. Hope it can be done using jade.

Here is my code:

index.jade:
body
  .wrapper
    include inc/header_piece

    append header
      .someextradiv
        | text

inc/header_piece.jade:
  block header
    .header
      a(href = '/') Home

What I expect to get:

<div class="wrapper">
  <div class="header"><a href="/">Home</a>
    <div class="someextradiv">Text</div>
  </div>
</div>

What I really get:

<div class="wrapper">
  <div class="header"><a href="/">Home</a></div>
  <div class="header"><a href="/">Home</a></div>
</div>

What I'm doing wrong and how to get desired result?