diff --git a/lisp/transient.el b/lisp/transient.el
index ed05c2d7..348f885e 100644
--- a/lisp/transient.el
+++ b/lisp/transient.el
@@ -498,7 +498,7 @@ See info node `(transient)Enabling and Disabling Suffixes'."
   :group 'transient-faces)
 
 (defface transient-higher-level
-  `((t (:box ( :line-width -1
+  `((t (:box ( :line-width ,(if (>= emacs-major-version 28) (cons -1 -1) -1)
                :color ,(face-attribute 'shadow :foreground nil t)))))
   "Face optionally used to highlight suffixes on higher levels.
 Also see option `transient-highlight-higher-levels'."
@@ -560,13 +560,15 @@ character used to separate possible values from each other."
   :group 'transient-faces)
 
 (defface transient-nonstandard-key
-  '((t (:box (:line-width -1 :color "cyan"))))
+  `((t (:box ( :line-width ,(if (>= emacs-major-version 28) (cons -1 -1) -1)
+               :color "cyan"))))
   "Face optionally used to highlight keys conflicting with short-argument.
 Also see option `transient-highlight-mismatched-keys'."
   :group 'transient-faces)
 
 (defface transient-mismatched-key
-  '((t (:box (:line-width -1 :color "magenta"))))
+  `((t (:box ( :line-width ,(if (>= emacs-major-version 28) (cons -1 -1) -1)
+               :color "magenta"))))
   "Face optionally used to highlight keys without a short-argument.
 Also see option `transient-highlight-mismatched-keys'."
   :group 'transient-faces)