1 files changed, 15 insertions, 1 deletions

diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index 98b0acfc0c6..a84a7b1c716 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -878,7 +878,21 @@ The optional NEW-WINDOW argument is not used."
            (error "Browsing URLs is not supported on this system")))
         ((eq system-type 'cygwin)
          (call-process "cygstart" nil nil nil url))
-        (t (w32-shell-execute "open" (url-unhex-string url)))))
+        (t
+         (w32-shell-execute "open"
+                            ;; w32-shell-execute passes file:// URLs
+                            ;; to APIs that expect file names, so we
+                            ;; need to unhex any %nn encoded
+                            ;; characters in the URL.  We don't do
+                            ;; that for other URLs; in particular,
+                            ;; default Windows mail client barfs on
+                            ;; quotes in the MAILTO URLs, so we prefer
+                            ;; to leave the URL with its embedded %nn
+                            ;; encoding intact.
+                            (if (eq t (compare-strings url nil 7
+                                                       "file://" nil nil))
+                                (url-unhex-string url)
+                              url)))))
 
 (defun browse-url-default-macosx-browser (url &optional _new-window)
   "Invoke the macOS system's default Web browser.