diff --git a/lib/common.js b/lib/common.js
index 5bdcb73..978cde9 100644
--- a/lib/common.js
+++ b/lib/common.js
@@ -93,7 +93,7 @@ class DocumentLocaleSettings {
 
 	constructor() {
 		this._cache = new Map();
-		this._htmlElem = window.document.getElementsByTagName('html')[0];
+		this._htmlElem = document.documentElement;
 		this._listeners = [];
 		this._overrides = {};
 		this._observer = new MutationObserver(this._handleObserverChange.bind(this));
@@ -227,8 +227,16 @@ export function getDocumentLocaleSettings() {
 	return documentLocaleSettings;
 }
 
+const localeRegEx = /[^a-zA-Z0-9-]/g;
+
 function updateLocalNames() {
-	const localName = new Intl.DisplayNames(documentLocaleSettings.language || navigator.language, { type: 'language' });
+	const possibleLocales = [documentLocaleSettings.language, navigator.language, defaultLocale].filter(l => l && !localeRegEx.test(l));
+	let localName;
+	try {
+		localName = new Intl.DisplayNames(possibleLocales, { type: 'language' });
+	} catch {
+		return;
+	}
 	supportedLocalesDetails.forEach(l => {
 		l.localName = localName.of(l.overrideCode || l.code);
 	});