diff --git a/mozilla/browser/base/content/browser.js b/mozilla/browser/base/content/browser.js
index f9531bd08c6..ad5a3ab5374 100644
--- a/mozilla/browser/base/content/browser.js
+++ b/mozilla/browser/base/content/browser.js
@@ -3135,6 +3135,14 @@ function BrowserToolboxCustomizeDone(aToolboxChanged)
         document.getElementById('Browser:Back').hasAttribute('disabled') &&
         document.getElementById('Browser:Forward').hasAttribute('disabled');
 
+    // support downgrading to Firefox 2.0
+    var navBar = document.getElementById("nav-bar");
+    navBar.setAttribute("currentset",
+                        navBar.getAttribute("currentset")
+                              .replace("unified-back-forward-button",
+                                "unified-back-forward-button,back-button,forward-button"));
+    document.persist(navBar.id, "currentset");
+
 #ifndef XP_MACOSX
     updateEditUIVisibility();
 #endif