diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 59a3de45..5ca84cab 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -78,10 +78,10 @@ class Backend {
         this._isPrepared = false;
         this._prepareError = false;
         this._preparePromise = null;
-        this._prepareCompletePromise = new Promise((resolve, reject) => {
-            this._prepareCompleteResolve = resolve;
-            this._prepareCompleteReject = reject;
-        });
+        const {promise, resolve, reject} = deferPromise();
+        this._prepareCompletePromise = promise;
+        this._prepareCompleteResolve = resolve;
+        this._prepareCompleteReject = reject;
 
         this._defaultBrowserActionTitle = null;
         this._badgePrepareDelayTimer = null;
@@ -1269,8 +1269,7 @@ class Backend {
     static async _findTab(timeout, checkUrl) {
         // This function works around the need to have the "tabs" permission to access tab.url.
         const tabs = await new Promise((resolve) => chrome.tabs.query({}, resolve));
-        let matchPromiseResolve = null;
-        const matchPromise = new Promise((resolve) => { matchPromiseResolve = resolve; });
+        const {promise: matchPromise, resolve: matchPromiseResolve} = deferPromise();
 
         const checkTabUrl = ({tab, url}) => {
             if (checkUrl(url, tab)) {
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 5ee62c9b..931813de 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -229,12 +229,11 @@ class Popup {
         return new Promise((resolve, reject) => {
             const tokenMap = new Map();
             let timer = null;
-            let frameLoadedResolve = null;
-            let frameLoadedReject = null;
-            const frameLoaded = new Promise((resolve2, reject2) => {
-                frameLoadedResolve = resolve2;
-                frameLoadedReject = reject2;
-            });
+            let {
+                promise: frameLoadedPromise,
+                resolve: frameLoadedResolve,
+                reject: frameLoadedReject
+            } = deferPromise();
 
             const postMessage = (action, params) => {
                 const contentWindow = frame.contentWindow;
@@ -261,7 +260,7 @@ class Popup {
                     if (!isObject(message)) { return; }
                     const {action, params} = message;
                     if (!isObject(params)) { return; }
-                    await frameLoaded;
+                    await frameLoadedPromise;
                     if (timer === null) { return; } // Done
 
                     switch (action) {
@@ -331,7 +330,7 @@ class Popup {
             frame.addEventListener('load', onLoad);
 
             // Prevent unhandled rejections
-            frameLoaded.catch(() => {}); // NOP
+            frameLoadedPromise.catch(() => {}); // NOP
 
             setupFrame(frame);
         });
diff --git a/ext/mixed/js/api.js b/ext/mixed/js/api.js
index 5c17d50e..1e421147 100644
--- a/ext/mixed/js/api.js
+++ b/ext/mixed/js/api.js
@@ -212,12 +212,11 @@ const api = (() => {
         _createActionPort(timeout=5000) {
             return new Promise((resolve, reject) => {
                 let timer = null;
-                let portNameResolve;
-                let portNameReject;
-                const portNamePromise = new Promise((resolve2, reject2) => {
-                    portNameResolve = resolve2;
-                    portNameReject = reject2;
-                });
+                const {
+                    promise: portNamePromise,
+                    resolve: portNameResolve,
+                    reject: portNameReject
+                } = deferPromise();
 
                 const onConnect = async (port) => {
                     try {
diff --git a/ext/mixed/js/core.js b/ext/mixed/js/core.js
index e22be33d..fec26a0e 100644
--- a/ext/mixed/js/core.js
+++ b/ext/mixed/js/core.js
@@ -197,6 +197,16 @@ const clone = (() => {
  * Async utilities
  */
 
+function deferPromise() {
+    let resolve;
+    let reject;
+    const promise = new Promise((resolve2, reject2) => {
+        resolve = resolve2;
+        reject = reject2;
+    });
+    return {promise, resolve, reject};
+}
+
 function promiseTimeout(delay, resolveValue) {
     if (delay <= 0) {
         const promise = Promise.resolve(resolveValue);
@@ -206,8 +216,7 @@ function promiseTimeout(delay, resolveValue) {
     }
 
     let timer = null;
-    let promiseResolve = null;
-    let promiseReject = null;
+    let {promise, resolve, reject} = deferPromise();
 
     const complete = (callback, value) => {
         if (callback === null) { return; }
@@ -215,39 +224,25 @@ function promiseTimeout(delay, resolveValue) {
             clearTimeout(timer);
             timer = null;
         }
-        promiseResolve = null;
-        promiseReject = null;
+        resolve = null;
+        reject = null;
         callback(value);
     };
 
-    const resolve = (value) => complete(promiseResolve, value);
-    const reject = (value) => complete(promiseReject, value);
+    const resolveWrapper = (value) => complete(resolve, value);
+    const rejectWrapper = (value) => complete(reject, value);
 
-    const promise = new Promise((resolve2, reject2) => {
-        promiseResolve = resolve2;
-        promiseReject = reject2;
-    });
     timer = setTimeout(() => {
         timer = null;
-        resolve(resolveValue);
+        resolveWrapper(resolveValue);
     }, delay);
 
-    promise.resolve = resolve;
-    promise.reject = reject;
+    promise.resolve = resolveWrapper;
+    promise.reject = rejectWrapper;
 
     return promise;
 }
 
-function deferPromise() {
-    let resolve;
-    let reject;
-    const promise = new Promise((resolve2, reject2) => {
-        resolve = resolve2;
-        reject = reject2;
-    });
-    return {promise, resolve, reject};
-}
-
 
 /*
  * Common events