diff --git a/chrome/content/zotero/elements/contextPane.js b/chrome/content/zotero/elements/contextPane.js
index 6b8ee474d8..553e600294 100644
--- a/chrome/content/zotero/elements/contextPane.js
+++ b/chrome/content/zotero/elements/contextPane.js
@@ -90,7 +90,7 @@
 				this._handleTabClose(action, type, ids, extraData);
 				return;
 			}
-			if (type == 'tab' && action == 'select') {
+			if (type == 'tab' && ["select", "load"].includes(action)) {
 				this._handleTabSelect(action, type, ids, extraData);
 			}
 		}
@@ -158,23 +158,24 @@
 			});
 		}
 
-		_handleTabSelect(action, type, ids) {
+		async _handleTabSelect(action, type, ids, extraData) {
 			// TEMP: move these variables to ZoteroContextPane
 			let _contextPaneSplitter = ZoteroContextPane.splitter;
 			let _contextPane = document.getElementById('zotero-context-pane');
+			let tabID = ids[0];
+			let tabType = extraData[tabID].type;
 			// It seems that changing `hidden` or `collapsed` values might
 			// be related with significant slow down when there are too many
 			// DOM nodes (i.e. 10k notes)
-			if (Zotero_Tabs.selectedType == 'library') {
+			if (tabType == 'library') {
 				_contextPaneSplitter.setAttribute('hidden', true);
 				_contextPane.setAttribute('collapsed', true);
 				ZoteroContextPane.showLoadingMessage(false);
 				this._sidenav.hidden = true;
 			}
-			else if (Zotero_Tabs.selectedType.includes('reader')) {
-				let reader = Zotero.Reader.getByTabID(Zotero_Tabs.selectedID);
-				this._handleReaderReady(reader);
-			
+			else if (tabType == 'reader') {
+				this._handleReaderReady(tabID);
+				this._setupNotesContext(tabID);
 				_contextPaneSplitter.setAttribute('hidden', false);
 
 				_contextPane.setAttribute('collapsed', !(_contextPaneSplitter.getAttribute('state') != 'collapsed'));
@@ -187,11 +188,26 @@
 				this._sidenav.hidden = false;
 			}
 
-			this._selectItemContext(ids[0]);
+			this._selectItemContext(tabID);
 			ZoteroContextPane.update();
 		}
 
-		async _handleReaderReady(reader) {
+		async _setupNotesContext(tabID) {
+			let { tab } = Zotero_Tabs._getTab(tabID);
+			if (!tab || !tab.data.itemID) return;
+			let attachment = await Zotero.Items.getAsync(tab.data.itemID);
+			if (attachment) {
+				this._selectNotesContext(attachment.libraryID);
+				let notesContext = this._getNotesContext(attachment.libraryID);
+				notesContext.updateNotesListFromCache();
+			}
+			let currentNoteContext = this._getCurrentNotesContext();
+			// Always switch to the current selected tab, since the selection might have changed
+			currentNoteContext.switchToTab(Zotero_Tabs.selectedID);
+		}
+
+		async _handleReaderReady(tabID) {
+			let reader = Zotero.Reader.getByTabID(tabID);
 			if (!reader) {
 				return;
 			}
@@ -209,16 +225,6 @@
 					});
 				}
 			}
-			
-			let attachment = await Zotero.Items.getAsync(reader.itemID);
-			if (attachment) {
-				this._selectNotesContext(attachment.libraryID);
-				let notesContext = this._getNotesContext(attachment.libraryID);
-				notesContext.updateNotesListFromCache();
-			}
-
-			let currentNoteContext = this._getCurrentNotesContext();
-			currentNoteContext.switchToTab(reader.tabID);
 		}
 
 		_getCurrentNotesContext() {
@@ -270,7 +276,7 @@
 			}
 		}
 	
-		async _addItemContext(tabID, itemID, tabType = "") {
+		async _addItemContext(tabID, itemID, _tabType = "") {
 			let { libraryID } = Zotero.Items.getLibraryAndKeyFromID(itemID);
 			let library = Zotero.Libraries.get(libraryID);
 			await library.waitForDataLoad('item');
diff --git a/chrome/content/zotero/standalone/standalone.js b/chrome/content/zotero/standalone/standalone.js
index 008ea491a0..089de41e2e 100644
--- a/chrome/content/zotero/standalone/standalone.js
+++ b/chrome/content/zotero/standalone/standalone.js
@@ -57,7 +57,7 @@ const ZoteroStandalone = new function() {
 		this._notifierID = Zotero.Notifier.registerObserver(
 			{
 				notify: async (action, type, ids, extraData) => {
-					if (action == 'select') {
+					if (['select', 'load'].includes(action)) {
 						// Reader doesn't have tabID yet
 						setTimeout(async () => {
 							// Item and other things might not be loaded yet when reopening tabs
diff --git a/chrome/content/zotero/tabs.js b/chrome/content/zotero/tabs.js
index 3c67762627..bd6a570701 100644
--- a/chrome/content/zotero/tabs.js
+++ b/chrome/content/zotero/tabs.js
@@ -456,6 +456,7 @@ var Zotero_Tabs = new function () {
 			selectedTab.lastFocusedElement = document.activeElement;
 		}
 		if (tab.type === 'reader-unloaded') {
+			tab.type = "reader-loading";
 			// Make sure the loading message is displayed first.
 			// Then, open reader and hide the loading message once it has loaded.
 			ZoteroContextPane.showLoadingMessage(true);
@@ -518,8 +519,10 @@ var Zotero_Tabs = new function () {
 	// Mark a tab as loaded
 	this.markAsLoaded = function (id) {
 		let { tab } = this._getTab(id);
-		if (!tab) return;
+		if (!tab || tab.type == "reader") return;
+		let prevType = tab.type;
 		tab.type = "reader";
+		Zotero.Notifier.trigger("load", "tab", [id], { [id]: Object.assign({}, tab, { prevType }) }, true);
 	};
 
 	this.unloadUnusedTabs = function () {
@@ -569,7 +572,7 @@ var Zotero_Tabs = new function () {
 		setTimeout(() => {
 			reader.focus();
 		});
-	}
+	};
 
 	/**
 	 * Moves focus to a tab in the specified direction.
diff --git a/chrome/content/zotero/xpcom/reader.js b/chrome/content/zotero/xpcom/reader.js
index 9dcd96410b..4e4293dcab 100644
--- a/chrome/content/zotero/xpcom/reader.js
+++ b/chrome/content/zotero/xpcom/reader.js
@@ -497,7 +497,7 @@ class ReaderInstance {
 				}
 			},
 			onToggleContextPane: () => {
-				Zotero.debug('toggle context pane')
+				Zotero.debug('toggle context pane');
 				let win = Zotero.getMainWindow();
 				win.ZoteroContextPane.togglePane();
 			},
@@ -1800,8 +1800,7 @@ class Reader {
 		let { libraryID } = Zotero.Items.getLibraryAndKeyFromID(itemID);
 		let library = Zotero.Libraries.get(libraryID);
 		let win = Zotero.getMainWindow();
-		// Change tab's type from "unloaded-reader" to "reader"
-		win.Zotero_Tabs.markAsLoaded(tabID);
+
 		await library.waitForDataLoad('item');
 
 		let item = Zotero.Items.get(itemID);
@@ -1885,6 +1884,8 @@ class Reader {
 				}
 			});
 			this._readers.push(reader);
+			// Change tab's type from "reader-unloaded" to "reader" after reader loaded
+			win.Zotero_Tabs.markAsLoaded(tabID);
 		}
 		
 		if (!openInBackground