Maybe it takes too much horizontal space? I don't know.
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diff --git a/lisp/term/x-win.el b/lisp/term/x-win.el
index 42a6f4030e..fa87739c23 100644
--- a/lisp/term/x-win.el
+++ b/lisp/term/x-win.el
@@ -1396,6 +1396,7 @@ x-gtk-stock-map
     ("etc/images/save" . ("document-save" "gtk-save"))
     ("etc/images/saveas" . ("document-save-as" "gtk-save-as"))
     ("etc/images/undo" . ("edit-undo" "gtk-undo"))
+    ("etc/images/redo" . ("edit-redo" "gtk-redo"))
     ("etc/images/cut" . ("edit-cut" "gtk-cut"))
     ("etc/images/copy" . ("edit-copy" "gtk-copy"))
     ("etc/images/paste" . ("edit-paste" "gtk-paste"))
diff --git a/lisp/tool-bar.el b/lisp/tool-bar.el
index 7df1e28e06..ac8134dce6 100644
--- a/lisp/tool-bar.el
+++ b/lisp/tool-bar.el
@@ -259,6 +259,7 @@ tool-bar-setup
                               :label "Save")
   (define-key-after (default-value 'tool-bar-map) [separator-1] menu-bar-separator)
   (tool-bar-add-item-from-menu 'undo "undo" nil)
+  (tool-bar-add-item-from-menu 'undo-redo "redo" nil)
   (define-key-after (default-value 'tool-bar-map) [separator-2] menu-bar-separator)
   (tool-bar-add-item-from-menu (lookup-key menu-bar-edit-menu [cut])
                               "cut" nil :vert-only t)
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