diff --git a/chrome/content/zotero/containers/tagSelector.jsx b/chrome/content/zotero/containers/tagSelector.jsx
index 834f46bfe9..ed6ca94408 100644
--- a/chrome/content/zotero/containers/tagSelector.jsx
+++ b/chrome/content/zotero/containers/tagSelector.jsx
@@ -26,7 +26,7 @@ Zotero.TagSelector = class TagSelectorContainer extends React.PureComponent {
 			['collection-item', 'item', 'item-tag', 'tag', 'setting'],
 			'tagSelector'
 		);
-		Zotero.Prefs.registerObserver('fontSize', this.handleFontChange.bind(this));
+		this._prefObserverID = Zotero.Prefs.registerObserver('fontSize', this.handleFontChange.bind(this));
 		
 		this.tagListRef = React.createRef();
 		this.searchBoxRef = React.createRef();
@@ -731,12 +731,8 @@ Zotero.TagSelector = class TagSelectorContainer extends React.PureComponent {
 	
 	uninit() {
 		ReactDOM.unmountComponentAtNode(this.domEl);
-		if (this._notifierID) {
-			Zotero.Notifier.unregisterObserver(this._notifierID);
-		}
-		if (this._prefObserverID) {
-			Zotero.Prefs.unregisterObserver('fontSize', this.handleFontChange.bind(this));
-		}
+		Zotero.Notifier.unregisterObserver(this._notifierID);
+		Zotero.Prefs.unregisterObserver(this._prefObserverID);
 	}
 	
 	static propTypes = {
diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index 6258e34403..42ed281fa5 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -53,12 +53,13 @@ Zotero.ItemTreeView = function (collectionTreeRow) {
 	
 	this._refreshPromise = Zotero.Promise.resolve();
 	
-	this._unregisterID = Zotero.Notifier.registerObserver( 
+	this._notifierObserverID = Zotero.Notifier.registerObserver(
 		this,
 		['item', 'collection-item', 'item-tag', 'share-items', 'bucket', 'feedItem', 'search'],
 		'itemTreeView',
 		50
 	);
+	this._prefObserverID = Zotero.Prefs.registerObserver('recursiveCollections', this.refresh.bind(this));
 }
 
 Zotero.ItemTreeView.prototype = Object.create(Zotero.LibraryTreeView.prototype);
@@ -1019,7 +1020,8 @@ Zotero.ItemTreeView.prototype.notify = Zotero.Promise.coroutine(function* (actio
 
 
 Zotero.ItemTreeView.prototype.unregister = async function() {
-	Zotero.Notifier.unregisterObserver(this._unregisterID);
+	Zotero.Notifier.unregisterObserver(this._notifierObserverID);
+	Zotero.Prefs.unregisterObserver(this._prefObserverID);
 	
 	if (this.collectionTreeRow.onUnload) {
 		await this.collectionTreeRow.onUnload();
diff --git a/chrome/content/zotero/xpcom/prefs.js b/chrome/content/zotero/xpcom/prefs.js
index c13926ba0b..a0df9a3c6b 100644
--- a/chrome/content/zotero/xpcom/prefs.js
+++ b/chrome/content/zotero/xpcom/prefs.js
@@ -274,24 +274,39 @@ Zotero.Prefs = new function(){
 	}
 	
 	var _observers = {};
-	this.registerObserver = function(name, handler) {
+	var _observersBySymbol = {};
+	
+	/**
+	 * @param {String} name - Preference name on extensions.zotero branch
+	 * @param {Function} handler
+	 * @return {Symbol} - Symbol to pass to unregisterObserver()
+	 */
+	this.registerObserver = function (name, handler) {
+		var symbol = Symbol();
 		_observers[name] = _observers[name] || [];
 		_observers[name].push(handler);
+		_observersBySymbol[symbol] = [name, handler];
+		return symbol;
 	}
 	
-	this.unregisterObserver = function(name, handler) {
-		var obs = _observers[name];
+	/**
+	 * @param {Symbol} symbol - Symbol returned from registerObserver()
+	 */
+	this.unregisterObserver = function (symbol) {
+		var obs = _observersBySymbol[symbol];
 		if (!obs) {
-			Zotero.debug("No preferences observer registered for " + name);
+			Zotero.debug("No pref observer registered for given symbol");
 			return;
 		}
 		
+		delete _observersBySymbol[symbol];
+		
+		var [name, handler] = obs;
 		var i = obs.indexOf(handler);
 		if (i == -1) {
-			Zotero.debug("Handler was not registered for preference " + name);
+			Zotero.debug("Handler was not registered for preference " + name, 2);
 			return;
 		}
-		
 		obs.splice(i, 1);
 	}
 }
diff --git a/chrome/content/zotero/xpcom/quickCopy.js b/chrome/content/zotero/xpcom/quickCopy.js
index f2542c0a83..a279d96d08 100644
--- a/chrome/content/zotero/xpcom/quickCopy.js
+++ b/chrome/content/zotero/xpcom/quickCopy.js
@@ -40,7 +40,9 @@ Zotero.QuickCopy = new function() {
 		
 		if (!_initialized) {
 			// Make sure export translator code is loaded whenever the output format changes
-			Zotero.Prefs.registerObserver("export.quickCopy.setting", _loadOutputFormat);
+			this._prefObserverID = Zotero.Prefs.registerObserver(
+				"export.quickCopy.setting", _loadOutputFormat
+			);
 			_initialized = true;
 		}
 		
@@ -71,7 +73,7 @@ Zotero.QuickCopy = new function() {
 		if (_initPromise) {
 			_initPromise.cancel();
 		}
-		Zotero.Prefs.unregisterObserver("export.quickCopy.setting", _loadOutputFormat);
+		Zotero.Prefs.unregisterObserver(this._prefObserverID);
 	};