diff --git a/app/ui.js b/app/ui.js
index aaabad72..67af7cda 100644
--- a/app/ui.js
+++ b/app/ui.js
@@ -39,22 +39,20 @@ const UI = {
     reconnect_callback: null,
     reconnect_password: null,
 
-    prime(callback) {
-        if (document.readyState === "interactive" || document.readyState === "complete") {
-            UI.load(callback);
-        } else {
-            document.addEventListener('DOMContentLoaded', UI.load.bind(UI, callback));
-        }
-    },
+    prime() {
+        return WebUtil.initSettings().then(() => {
+            if (document.readyState === "interactive" || document.readyState === "complete") {
+                return UI.start();
+            }
 
-    // Setup rfb object, load settings from browser storage, then call
-    // UI.init to setup the UI/menus
-    load(callback) {
-        WebUtil.initSettings(UI.start, callback);
+            return new Promise((resolve, reject) => {
+                document.addEventListener('DOMContentLoaded', () => UI.start().then(resolve).catch(reject));
+            });
+        });
     },
 
     // Render default UI and initialize settings menu
-    start(callback) {
+    start() {
 
         UI.initSettings();
 
@@ -105,9 +103,7 @@ const UI = {
             UI.openConnectPanel();
         }
 
-        if (typeof callback === "function") {
-            callback(UI.rfb);
-        }
+        return Promise.resolve(UI.rfb);
     },
 
     initFullscreen() {
@@ -1646,18 +1642,13 @@ const UI = {
 // Set up translations
 const LINGUAS = ["cs", "de", "el", "es", "ko", "nl", "pl", "sv", "tr", "zh_CN", "zh_TW"];
 l10n.setup(LINGUAS);
-if (l10n.language !== "en" && l10n.dictionary === undefined) {
-    WebUtil.fetchJSON('app/locale/' + l10n.language + '.json', (translations) => {
-        l10n.dictionary = translations;
-
-        // wait for translations to load before loading the UI
-        UI.prime();
-    }, (err) => {
-        Log.Error("Failed to load translations: " + err);
-        UI.prime();
-    });
-} else {
+if (l10n.language === "en" || l10n.dictionary !== undefined) {
     UI.prime();
+} else {
+    WebUtil.fetchJSON('app/locale/' + l10n.language + '.json')
+        .then((translations) => { l10n.dictionary = translations; })
+        .catch(err => Log.Error("Failed to load translations: " + err))
+        .then(UI.prime);
 }
 
 export default UI;
diff --git a/app/webutil.js b/app/webutil.js
index 922ddc10..98e1d9e6 100644
--- a/app/webutil.js
+++ b/app/webutil.js
@@ -114,22 +114,14 @@ export function eraseCookie(name) {
 
 let settings = {};
 
-export function initSettings(callback /*, ...callbackArgs */) {
-    "use strict";
-    const callbackArgs = Array.prototype.slice.call(arguments, 1);
-    if (window.chrome && window.chrome.storage) {
-        window.chrome.storage.sync.get((cfg) => {
-            settings = cfg;
-            if (callback) {
-                callback.apply(this, callbackArgs);
-            }
-        });
-    } else {
+export function initSettings() {
+    if (!window.chrome || !window.chrome.storage) {
         settings = {};
-        if (callback) {
-            callback.apply(this, callbackArgs);
-        }
+        return Promise.resolve();
     }
+
+    return new Promise(resolve => window.chrome.storage.sync.get(resolve))
+        .then((cfg) => { settings = cfg; });
 }
 
 // Update the settings cache, but do not write to permanent storage
@@ -218,28 +210,30 @@ export function injectParamIfMissing(path, param, value) {
 // IE11 support or polyfill promises and fetch in IE11.
 // resolve will receive an object on success, while reject
 // will receive either an event or an error on failure.
-export function fetchJSON(path, resolve, reject) {
-    // NB: IE11 doesn't support JSON as a responseType
-    const req = new XMLHttpRequest();
-    req.open('GET', path);
+export function fetchJSON(path) {
+    return new Promise((resolve, reject) => {
+        // NB: IE11 doesn't support JSON as a responseType
+        const req = new XMLHttpRequest();
+        req.open('GET', path);
 
-    req.onload = () => {
-        if (req.status === 200) {
-            let resObj;
-            try {
-                resObj = JSON.parse(req.responseText);
-            } catch (err) {
-                reject(err);
+        req.onload = () => {
+            if (req.status === 200) {
+                let resObj;
+                try {
+                    resObj = JSON.parse(req.responseText);
+                } catch (err) {
+                    reject(err);
+                }
+                resolve(resObj);
+            } else {
+                reject(new Error("XHR got non-200 status while trying to load '" + path + "': " + req.status));
             }
-            resolve(resObj);
-        } else {
-            reject(new Error("XHR got non-200 status while trying to load '" + path + "': " + req.status));
-        }
-    };
+        };
 
-    req.onerror = evt => reject(new Error("XHR encountered an error while trying to load '" + path + "': " + evt.message));
+        req.onerror = evt => reject(new Error("XHR encountered an error while trying to load '" + path + "': " + evt.message));
 
-    req.ontimeout = evt => reject(new Error("XHR timed out while trying to load '" + path + "'"));
+        req.ontimeout = evt => reject(new Error("XHR timed out while trying to load '" + path + "'"));
 
-    req.send();
+        req.send();
+    });
 }
diff --git a/tests/test.webutil.js b/tests/test.webutil.js
index 27397041..72e19421 100644
--- a/tests/test.webutil.js
+++ b/tests/test.webutil.js
@@ -39,7 +39,7 @@ describe('WebUtil', function () {
                 window.localStorage.getItem = sinon.stub();
                 window.localStorage.removeItem = sinon.stub();
 
-                WebUtil.initSettings();
+                return WebUtil.initSettings();
             });
             afterEach(function () {
                 Object.defineProperty(window, "localStorage", origLocalStorage);
@@ -132,7 +132,7 @@ describe('WebUtil', function () {
                 settings = {};
                 csSandbox.spy(window.chrome.storage.sync, 'set');
                 csSandbox.spy(window.chrome.storage.sync, 'remove');
-                WebUtil.initSettings();
+                return WebUtil.initSettings();
             });
             afterEach(function () {
                 csSandbox.restore();