diff --git a/chrome/content/zotero/tabs.js b/chrome/content/zotero/tabs.js
index 726277d8d9..0772b3317e 100644
--- a/chrome/content/zotero/tabs.js
+++ b/chrome/content/zotero/tabs.js
@@ -77,10 +77,10 @@ var Zotero_Tabs = new function () {
 	this._focusOptions = {};
 
 	// Keep track of item modifications to update the title
-	Zotero.Notifier.registerObserver(this, ['item'], 'tabs');
+	this._notifierID = Zotero.Notifier.registerObserver(this, ['item'], 'tabs');
 
 	// Update the title when pref of title format is changed
-	Zotero.Prefs.registerObserver('tabs.title.reader', async () => {
+	this._prefsObserverID = Zotero.Prefs.registerObserver('tabs.title.reader', async () => {
 		for (let tab of this._tabs) {
 			if (!tab.data.itemID) continue;
 			let item = Zotero.Items.get(tab.data.itemID);
@@ -88,6 +88,11 @@ var Zotero_Tabs = new function () {
 			this.rename(tab.id, title);
 		}
 	});
+	
+	window.addEventListener('unload', () => {
+		Zotero.Notifier.unregisterObserver(this._notifierID);
+		Zotero.Prefs.unregisterObserver(this._prefsObserverID);
+	});
 
 	this._unloadInterval = setInterval(() => {
 		this.unloadUnusedTabs();