When fast-scroll is active, winum modeline text disappears

[winny-]

When fast-scroll-mode is active, and it is triggered (e.g. hold down C-v), the winum number in the left modeline disappears until fast-scroll disengaged. Not sure if this is a bug in fast-scroll or winum.

I tested with the below init.el and visited a large file (such as linux/mm/mmap.c) and held down C-v.

demo

init.el

;; From https://github.com/raxod502/straight.el#getting-started
(defvar bootstrap-version)
(let ((bootstrap-file
       (expand-file-name "straight/repos/straight.el/bootstrap.el" user-emacs-directory))
      (bootstrap-version 5))
  (unless (file-exists-p bootstrap-file)
    (with-current-buffer
        (url-retrieve-synchronously
         "https://raw.githubusercontent.com/raxod502/straight.el/develop/install.el"
         'silent 'inhibit-cookies)
      (goto-char (point-max))
      (eval-print-last-sexp)))
  (load bootstrap-file nil 'nomessage))

(straight-use-package 'use-package)

(use-package winum
  :straight t
  :init
  (winum-mode 1))

(use-package fast-scroll
  :straight t
  :init
  (fast-scroll-config)
  (fast-scroll-mode 1))

[winny-]

I found a way to work around this—override the definition of fast-scroll-default-mode-line like so:

(defun fast-scroll-default-mode-line ()
    mode-line-format)

Perhaps this should be considered a bug with fast-scroll, or not a bug at all…