(advice-remove 'kill-emacs 'spacemacs-really-exit)
(defun ad-advice-kill-emacs (orig-fun)
  "Prompt before killing."
  (if (and (not spacemacs-really-kill-emacs)
           (spacemacs/persistent-server-running-p))
      (when (y-or-n-p "Really kill frame?")
        (spacemacs/frame-killer))
    (when (y-or-n-p "Really exit?")
      (funcall orig-fun))))
(advice-add 'kill-emacs :around 'ad-advice-kill-emacs)