How to setup a simple face in 24.2

[Thierry Volpiatto <thierry.volpiatto@gmail.com>]

Hi, the title says all.
I have this face that behave differently in customize interface
depending the emacs version I use:

#+BEGIN_SRC lisp
(defface helm-grep-file
    '((t (:foreground "BlueViolet"
          :underline t)))
  "Face used to highlight grep results filenames."
  :group 'helm-grep)

#+END_SRC

emacs-24.1:

--8<---------------cut here---------------start------------->8---
Hide Helm Grep File face: [sample]
    State : STANDARD.
   Face used to highlight grep results filenames.
   [X] Underline: Value Menu On
   [X] Foreground: BlueViolet  Choose   (sample)
   Show All Attributes
--8<---------------cut here---------------end--------------->8---

emacs-24.2:

--8<---------------cut here---------------start------------->8---
Hide Helm Grep File face: [sample]
    State : STANDARD.
   Face used to highlight grep results filenames.
Lisp expression: 
((t
  (:underline t :foreground "BlueViolet")))
--8<---------------cut here---------------end--------------->8---

Thanks.

-- 
  Thierry
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