diff --git a/server/src/l10n.js b/server/src/l10n.js
index b357cdcca7..e6bd0fb496 100644
--- a/server/src/l10n.js
+++ b/server/src/l10n.js
@@ -46,19 +46,12 @@ exports.init = function(localeStringMap) {
   return initPromise;
 };
 
-exports.getText = function(locales, userAgent) {
+exports.getText = function(locales) {
   const bundles = {};
   const availableLocales = exports.getUserLocales(locales);
 
-  // This is a temporary fix for https://github.com/mozilla-services/screenshots/issues/4863
-  // to be reverted in https://github.com/mozilla-services/screenshots/issues/4993
-  let useIsolating = true;
-  if (userAgent && userAgent.includes("Win")) {
-    useIsolating = false;
-  }
-
   availableLocales.forEach((locale) => {
-    bundles[locale] = getFluentBundle(locale, useIsolating);
+    bundles[locale] = getFluentBundle(locale);
   });
 
   return function(l10nID, args) {
@@ -99,9 +92,9 @@ function useLocaleData(localeStringMap) {
   return initPromise;
 }
 
-function getFluentBundle(locale, useIsolating) {
+function getFluentBundle(locale) {
   if (!fluentBundles[locale]) {
-    const bundle = new FluentBundle(locale, {useIsolating});
+    const bundle = new FluentBundle(locale);
     bundle.addMessages(rawStrings[locale]);
     fluentBundles[locale] = bundle;
   }
diff --git a/server/src/middleware/l10n.js b/server/src/middleware/l10n.js
index ac8290690a..16797a8592 100644
--- a/server/src/middleware/l10n.js
+++ b/server/src/middleware/l10n.js
@@ -17,7 +17,7 @@ exports.getLanguages = function(req) {
 exports.l10n = function(req, res, next) {
   l10n.init().then(() => {
     const languages = exports.getLanguages(req);
-    req.getText = l10n.getText(languages, req.headers["user-agent"]);
+    req.getText = l10n.getText(languages);
     req.userLocales = l10n.getUserLocales(languages);
     req.messages = l10n.getStrings(languages);
     next();
diff --git a/server/src/reactruntime.js b/server/src/reactruntime.js
index 7c1369134b..c3aaab65e0 100644
--- a/server/src/reactruntime.js
+++ b/server/src/reactruntime.js
@@ -8,15 +8,13 @@ require("fluent-intl-polyfill/compat");
 const { FluentBundle } = require("fluent/compat");
 const { LocalizationProvider } = require("fluent-react/compat");
 const { getLocaleMessages } = require("./locale-messages");
-const bundles = [];
 
 function generateBundles(messages, locales) {
+  const bundles = [];
   for (const locale of locales) {
-    if (!messages[locale]) {
-      const bundle = new FluentBundle(locale);
-      bundle.addMessages(messages[locale]);
-      bundles.push(bundle);
-    }
+    const bundle = new FluentBundle(locale);
+    bundle.addMessages(messages[locale]);
+    bundles.push(bundle);
   }
   return bundles;
 }