diff --git a/chrome/content/zotero/preferences/preferences.js b/chrome/content/zotero/preferences/preferences.js
index 9a5e95be28..2eb9fa29a8 100644
--- a/chrome/content/zotero/preferences/preferences.js
+++ b/chrome/content/zotero/preferences/preferences.js
@@ -124,22 +124,6 @@ var Zotero_Preferences = {
 		}
 	},
 
-	/**
-	 * Opens a URI in the basic viewer
-	 */
-	openInViewer: function (uri) {
-		var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-			.getService(Components.interfaces.nsIWindowMediator);
-		var win = wm.getMostRecentWindow("zotero:basicViewer");
-		if (win) {
-			win.loadURI(uri);
-		}
-		else {
-			window.openDialog("chrome://zotero/content/standalone/basicViewer.xhtml",
-				"basicViewer", "chrome,resizable,centerscreen,menubar,scrollbars", uri);
-		}
-	},
-
 	_onNavigationSelect() {
 		for (let child of this.content.children) {
 			if (child !== this.helpContainer) {
diff --git a/chrome/content/zotero/preferences/preferences_advanced.xhtml b/chrome/content/zotero/preferences/preferences_advanced.xhtml
index 7c48815986..e54779b4df 100644
--- a/chrome/content/zotero/preferences/preferences_advanced.xhtml
+++ b/chrome/content/zotero/preferences/preferences_advanced.xhtml
@@ -253,10 +253,10 @@
 		<hbox id="zotero-prefpane-advanced-open-buttons" align="center">
 			<button id="config-editor"
 				label="&zotero.preferences.configEditor;"
-				oncommand="Zotero_Preferences.openInViewer('about:config')"/>
+				oncommand="Zotero.openInViewer('about:config')"/>
 			<button id="memory-info"
 				label="Memory Info"
-				oncommand="Zotero_Preferences.openInViewer('about:memory')"
+				oncommand="Zotero.openInViewer('about:memory')"
 				hidden="true"/>
 		</hbox>
 	</vbox>
diff --git a/chrome/content/zotero/preferences/preferences_cite.xhtml b/chrome/content/zotero/preferences/preferences_cite.xhtml
index ee26073f25..9be73bdaa7 100644
--- a/chrome/content/zotero/preferences/preferences_cite.xhtml
+++ b/chrome/content/zotero/preferences/preferences_cite.xhtml
@@ -61,10 +61,10 @@
 			<hbox>
 				<button id="openCSLEdit"
 					label="&zotero.preferences.styleEditor;"
-					oncommand="Zotero_Preferences.openInViewer('chrome://zotero/content/tools/csledit.xhtml', true)"/>
+					oncommand="Zotero.openInViewer('chrome://zotero/content/tools/csledit.xhtml', true)"/>
 				<button id="openCSLPreview"
 					label="&zotero.preferences.stylePreview;"
-					oncommand="Zotero_Preferences.openInViewer('chrome://zotero/content/tools/cslpreview.xhtml', true)"/>
+					oncommand="Zotero.openInViewer('chrome://zotero/content/tools/cslpreview.xhtml', true)"/>
 			</hbox>
 		</groupbox>
 	</vbox>
diff --git a/chrome/content/zotero/standalone/basicViewer.js b/chrome/content/zotero/standalone/basicViewer.js
index 5b408bd766..1e701d3008 100644
--- a/chrome/content/zotero/standalone/basicViewer.js
+++ b/chrome/content/zotero/standalone/basicViewer.js
@@ -52,6 +52,7 @@ window.addEventListener("load", /*async */function () {
 	//browser.docShellIsActive = false;
 
 	// Load URI passed in as nsISupports .data via openWindow()
+	window.viewerOriginalURI = window.arguments[0];
 	loadURI(window.arguments[0]);
 }, false);
 
diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index dd2ee06a52..b523fb9a99 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -1090,21 +1090,22 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 	 * @param {Function} [onLoad] - Function to run once URI is loaded; passed the loaded document
 	 */
 	this.openInViewer = function (uri, onLoad) {
-		var wm = Services.wm;
-		var win = wm.getMostRecentWindow("zotero:basicViewer");
-		if (win) {
-			win.loadURI(uri);
-		} else {
-			let ww = Components.classes['@mozilla.org/embedcomp/window-watcher;1']
-				.getService(Components.interfaces.nsIWindowWatcher);
-			let arg = Components.classes["@mozilla.org/supports-string;1"]
-				.createInstance(Components.interfaces.nsISupportsString);
-			arg.data = uri;
-			win = ww.openWindow(null, "chrome://zotero/content/standalone/basicViewer.xhtml",
-				"basicViewer", "chrome,dialog=yes,resizable,centerscreen,menubar,scrollbars", arg);
+		var viewerWins = Services.wm.getEnumerator("zotero:basicViewer");
+		for (let existingWin of viewerWins) {
+			if (existingWin.viewerOriginalURI === uri) {
+				existingWin.focus();
+				return;
+			}
 		}
+		let ww = Components.classes['@mozilla.org/embedcomp/window-watcher;1']
+			.getService(Components.interfaces.nsIWindowWatcher);
+		let arg = Components.classes["@mozilla.org/supports-string;1"]
+			.createInstance(Components.interfaces.nsISupportsString);
+		arg.data = uri;
+		let win = ww.openWindow(null, "chrome://zotero/content/standalone/basicViewer.xhtml",
+			null, "chrome,dialog=yes,resizable,centerscreen,menubar,scrollbars", arg);
 		if (onLoad) {
-			let browser
+			let browser;
 			let func = function () {
 				win.removeEventListener("load", func);
 				// <browser> is created in basicViewer.js in a window load event, so we have to