prog-mode-hook not run for C++ mode

Question

I am trying to turn on linum-mode and fci-mode for C++ editing. Here is my configuration:

;; If non nil line numbers are turned on in all `prog-mode' and `text-mode'
;; derivatives. If set to `relative', also turns on relative line numbers.
;; (default nil)
dotspacemacs-line-numbers t

The following is included in dotspacemacs/user-init ():

;; Activate column indicator in prog-mode and text-mode, except for org-mode
(add-hook 'prog-mode-hook 'turn-on-fci-mode)
(add-hook 'text-mode-hook 'turn-on-fci-mode)
(add-hook 'org-mode-hook 'turn-off-fci-mode 'append)

which should work according to https://github.com/syl20bnr/spacemacs/issues/4741. However the linum and fci modes are turned on for lisp but not for C++ mode. Anyone knows why?

My emacs version:

$ emacs --version
GNU Emacs 25.1.91.1
Copyright (C) 2016 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GNU Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING.