diff --git a/README.org b/README.org
index d242568..914826c 100644
--- a/README.org
+++ b/README.org
@@ -268,9 +268,10 @@ Several options are available through Emacs' Customize interface under
 
   Default: '(" *which-key*")
 
-- =winum-ignored-buffers-regex=
+- =winum-ignored-buffers-regexp=
 
-  List of regexes. Matching buffers will be ignored when assigning numbers.
+  List of regexps for buffer names. Matching buffers will be ignored when
+  assigning numbers. See [[https://www.gnu.org/software/emacs/manual/html_node/emacs/Regexps.html][Emacs' documentation on regexps]] for syntax.
 
   Default: '()
 
@@ -320,7 +321,8 @@ available winum options.
         winum-auto-setup-mode-line        t
         winum-format                      " %s "
         winum-mode-line-position          1
-        winum-ignored-buffers             '(" *which-key*"))
+        winum-ignored-buffers             '(" *which-key*")
+        winum-ignored-buffers-regexp      '(" \\*Treemacs-.*"))
 
   (winum-mode)
 #+END_SRC
diff --git a/winum.el b/winum.el
index 40839ff..599030a 100644
--- a/winum.el
+++ b/winum.el
@@ -155,8 +155,9 @@ result of `winum-get-number-string'."
   :group 'winum
   :type  '(repeat string))
 
-(defcustom winum-ignored-buffers-regex '()
-  "List of regex for buffers to ignore when assigning numbers."
+(defcustom winum-ignored-buffers-regexp '()
+  "List of regexps for buffer names to ignore when assigning numbers.
+See Info node `(emacs) Regexps' or Info node `(elisp) Regular Expressions'"
   :group 'winum
   :type '(repeat string)
   :risky t)
@@ -547,7 +548,7 @@ windows, however a higher number can be reserved by the user-defined
         (member (buffer-name (window-buffer window)) winum-ignored-buffers)
         (cl-some
          (lambda (regex) (string-match regex (buffer-name (window-buffer window))))
-         winum-ignored-buffers-regex))))
+         winum-ignored-buffers-regexp))))
 
 (defun winum--list-windows-in-frame (&optional f)
   "List windows in frame F using natural Emacs ordering."