[O] tangling files on export not working properly

[mcg]

Hello,

When exporting my document to latex I want org-mode to tangle a few code 
blocks.

#+NAME: tangle_files
#+BEGIN_SRC emacs-lisp :exports results :eval query-export

(org-babel-tangle-file "~/thesis/chapter/NH.org")

#+END_SRC

When I run the code block manually it works fine
*Messages*: "Tangled 2 code blocks from NH.org"

However, even though the is run on export, nothing gets tangled:
"Tangled 0 code blocks from 04.NH.org"

Is there any explanation for this? Anything I'm overlooking?