diff --git a/src/ZenCommonUtils.mjs b/src/ZenCommonUtils.mjs
index e2bd80f..cf8aec9 100644
--- a/src/ZenCommonUtils.mjs
+++ b/src/ZenCommonUtils.mjs
@@ -43,6 +43,13 @@ class ZenMultiWindowFeature {
 class ZenDOMOperatedFeature {
   constructor() {
     var initBound = this.init.bind(this);
-    window.addEventListener('DOMContentLoaded', initBound, { once: true });
+    document.addEventListener('DOMContentLoaded', initBound, { once: true });
+  }
+}
+
+class ZenPreloadedFeature {
+  constructor() {
+    var initBound = this.init.bind(this);
+    document.addEventListener('MozBeforeInitialXULLayout', initBound, { once: true });
   }
 }
diff --git a/src/ZenPinnedTabManager.mjs b/src/ZenPinnedTabManager.mjs
index 2552219..dcf940a 100644
--- a/src/ZenPinnedTabManager.mjs
+++ b/src/ZenPinnedTabManager.mjs
@@ -1,15 +1,15 @@
 {
   const lazy = {};
 
-  XPCOMUtils.defineLazyPreferenceGetter(lazy, 'zenPinnedTabRestorePinnedTabsToPinnedUrl', 'zen.pinned-tab-manager.restore-pinned-tabs-to-pinned-url', false);
-  XPCOMUtils.defineLazyPreferenceGetter(lazy, 'zenPinnedTabCloseShortcutBehavior', 'zen.pinned-tab-manager.close-shortcut-behavior', 'switch');
-
   class ZenPinnedTabsObserver {
     static ALL_EVENTS = ['TabPinned', 'TabUnpinned'];
 
     #listeners = [];
 
     constructor() {
+      XPCOMUtils.defineLazyPreferenceGetter(lazy, 'zenPinnedTabRestorePinnedTabsToPinnedUrl', 'zen.pinned-tab-manager.restore-pinned-tabs-to-pinned-url', false);
+      XPCOMUtils.defineLazyPreferenceGetter(lazy, 'zenPinnedTabCloseShortcutBehavior', 'zen.pinned-tab-manager.close-shortcut-behavior', 'switch');
+    
       this.#listenPinnedTabEvents();
     }
 
@@ -36,7 +36,7 @@
     }
   }
 
-  class ZenPinnedTabManager {
+  class ZenPinnedTabManager extends ZenPreloadedFeature {
     init() {
       this.observer = new ZenPinnedTabsObserver();
       this._initClosePinnedTabShortcut();