diff --git a/keybindings.el b/keybindings.el
index 30c4152..da642ce 100644
--- a/keybindings.el
+++ b/keybindings.el
@@ -34,6 +34,10 @@
 (global-set-key (kbd "C-c /") 'comment-or-uncomment-region-or-line)
 (global-set-key (kbd "C-c C-/") 'comment-or-uncomment-region-or-line)
 
+(when (require 'undo-tree nil 'noerror)
+  (global-set-key (kbd "M--") 'undo-tree-undo)
+  (global-set-key (kbd "M-_") 'undo-tree-redo))
+
 ;; Mac OS X specific keybindings
 (when (eq system-type 'darwin)