diff --git a/browser/base/content/browser-init.js b/browser/base/content/browser-init.js
index bee5309c04775adff8652bfe6c54b2d466e821ac..cfeaf7cf2e98c35e76bdd5451f90b004a04d4474 100644
--- a/browser/base/content/browser-init.js
+++ b/browser/base/content/browser-init.js
@@ -143,13 +143,15 @@ var gBrowserInit = {
     gNavToolbox.palette = document.getElementById(
       "BrowserToolbarPalette"
     ).content;
+    ZenCustomizableUI.init(window);
     for (let area of CustomizableUI.areas) {
       let type = CustomizableUI.getAreaType(area);
-      if (type == CustomizableUI.TYPE_TOOLBAR) {
+      if (type == CustomizableUI.TYPE_TOOLBAR && !area.startsWith("zen-")) {
         let node = document.getElementById(area);
         CustomizableUI.registerToolbarNode(node);
       }
     }
+    ZenCustomizableUI.registerToolbarNodes(window);
     BrowserSearch.initPlaceHolder();
 
     // Hack to ensure that the various initial pages favicon is loaded
@@ -239,6 +241,10 @@ var gBrowserInit = {
     gPrivateBrowsingUI.init();
     BrowserSearch.init();
     BrowserPageActions.init();
+
+    Services.scriptloader.loadSubScript("chrome://browser/content/ZenStartup.mjs", window);
+    Services.scriptloader.loadSubScript("chrome://browser/content/zenThemeModifier.js", window);
+
     if (gToolbarKeyNavEnabled) {
       ToolbarKeyboardNavigator.init();
     }