default behavior for multiple \header{}s

[Graham Percival]

From the manual, 10.3.1,
http://www.lilypond.org/doc/v2.7/Documentation/user/lilypond/Creating- 
titles.html
-----
As demonstrated before, you can use multiple \header blocks. When same  
fields appear in different blocks, the latter is used. Here is a short  
example.

\header {
  composer = "Composer"
}
\header {
  title = "Title"
}
\score {
  \new Staff { c'4 }
  \header {
    title = "New title"  % overwrite previous one
  }
}
-----

However, this example does _not_ overwrite the previous definition of  
title with "New title".  (at least, not in 2.7.38)  Is this intentional  
or a bug?
- Graham