diff --git a/diff-hl-show-hunk-inline.el b/diff-hl-show-hunk-inline.el
index 3b5214bb..174a2820 100644
--- a/diff-hl-show-hunk-inline.el
+++ b/diff-hl-show-hunk-inline.el
@@ -105,6 +105,10 @@ Compute it from LINES starting at INDEX with a WINDOW-SIZE."
          (index (min index (- len window-size))))
     (diff-hl-show-hunk-inline--splice lines index window-size)))
 
+(defun diff-hl-show-hunk-inline--underline-face ()
+  "Return the face used for inline popup underlines."
+  `(:underline ,(if (>= emacs-major-version 29) '(:position t) t)))
+
 (defun diff-hl-show-hunk-inline--compute-header (width &optional header)
   "Compute the header of the popup.
 Compute it from some WIDTH, and some optional HEADER text."
@@ -115,7 +119,7 @@ Compute it from some WIDTH, and some optional HEADER text."
          (new-width (- width (length header) (length scroll-indicator)))
          (line (propertize (concat (diff-hl-show-hunk-inline--separator new-width)
                                    header scroll-indicator )
-                           'face '(:underline t))))
+                           'face (diff-hl-show-hunk-inline--underline-face))))
     (concat line "\n") ))
 
 (defun diff-hl-show-hunk-inline--compute-footer (width &optional footer)
@@ -133,7 +137,7 @@ Compute it from some WIDTH, and some optional FOOTER text."
          (blank-line (if (display-graphic-p)
                          ""
                        (concat "\n" (propertize (diff-hl-show-hunk-inline--separator width)
-                                                'face '(:underline t)))))
+                                                'face (diff-hl-show-hunk-inline--underline-face)))))
          (line (propertize (concat (diff-hl-show-hunk-inline--separator new-width)
                                    footer scroll-indicator)
                            'face '(:overline t))))