diff --git a/config.el b/config.el
index 4016712..792717c 100644
--- a/config.el
+++ b/config.el
@@ -161,6 +161,27 @@
   ;; via ssh. This has to be added last so that it is the first element.
   (add-to-list 'tramp-default-proxies-alist '("localhost" "\\`root\\'" nil)))
 
+;; Configure undo-tree.
+(after! undo-tree
+  ;; Doom just gives up on the diff visualizer, because it is impossible to work
+  ;; around undo-tree's window management opinions in a consistent way. For now,
+  ;; hack it to work in some sensible way.
+  (defadvice! +undo-tree-visualizer-show-diff-a (fn &rest args)
+    "Display the undo-tree diff buffer underneath undo-tree's parent buffer."
+    :around #'undo-tree-visualizer-show-diff
+    (defadvice! +undo-tree-visualizer-diff-split-window-a (&rest _)
+      "Hack `split-window' to open the diff window where we want it."
+      :filter-args #'split-window
+      (list (get-buffer-window undo-tree-visualizer-parent-buffer) nil 'below))
+    (apply fn args)
+    (advice-remove 'split-window #'+undo-tree-visualizer-diff-split-window-a))
+  (setq
+   ;; Don't keep persistent history - that's what git is for.
+   undo-tree-auto-save-history nil
+   ;; This is nice, but this variables turns nil for some reason after leaving
+   ;; undo-tree. A more consistent experience is to just toggle it with "d".
+   undo-tree-visualizer-diff nil))
+
 ;; The only thing I actually missed from helm.
 (map! (:when (featurep! :completion vertico)
        :map vertico-map