diff --git a/src/sao.js b/src/sao.js
index b7f8ba5e1d..5a80bc3647 100644
--- a/src/sao.js
+++ b/src/sao.js
@@ -80,6 +80,17 @@ var Sao = {};
         })()
     });
 
+    window.onbeforeunload = function(e) {
+        if (Sao.main_menu_screen) {
+            Sao.main_menu_screen.save_tree_state(true);
+        }
+        if (Sao.Tab.tabs.length) {
+            var dialog = Sao.i18n.gettext("Are your sure to leave?");
+            e.returnValue = dialog;
+            return dialog;
+        }
+    };
+
     Sao.class_ = function(Parent, props) {
         var ClassConstructor = function() {
             if (!(this instanceof ClassConstructor))