diff --git a/src/client.js b/src/client.js
index 679b34d53..9ebdfd2d6 100644
--- a/src/client.js
+++ b/src/client.js
@@ -3870,7 +3870,7 @@ MatrixClient.prototype.setRoomMutePushRule = function(scope, roomId, mute) {
         } else if (!hasDontNotifyRule) {
             // Remove the existing one before setting the mute push rule
             // This is a workaround to SYN-590 (Push rule update fails)
-            deferred = Promise.defer();
+            deferred = utils.defer();
             this.deletePushRule(scope, "room", roomPushRule.rule_id)
             .done(function() {
                 self.addPushRule(scope, "room", roomId, {
diff --git a/src/store/indexeddb-remote-backend.js b/src/store/indexeddb-remote-backend.js
index 920739b6e..270bef961 100644
--- a/src/store/indexeddb-remote-backend.js
+++ b/src/store/indexeddb-remote-backend.js
@@ -17,6 +17,7 @@ limitations under the License.
 
 import Promise from 'bluebird';
 import logger from '../logger';
+import {defer} from '../utils';
 
 /**
  * An IndexedDB store backend where the actual backend sits in a web
@@ -152,7 +153,7 @@ RemoteIndexedDBStoreBackend.prototype = {
         // the promise automatically gets rejected
         return Promise.resolve().then(() => {
             const seq = this._nextSeq++;
-            const def = Promise.defer();
+            const def = defer();
 
             this._inFlight[seq] = def;
 
diff --git a/src/utils.js b/src/utils.js
index 4bea67129..f4887ac32 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -714,3 +714,16 @@ module.exports.ensureNoTrailingSlash = function(url) {
 module.exports.sleep = (ms, value) => new Promise((resolve => {
     setTimeout(resolve, ms, value);
 }));
+
+// Returns a Deferred
+module.exports.defer = () => {
+    let resolve;
+    let reject;
+
+    const promise = new Promise((_resolve, _reject) => {
+        resolve = _resolve;
+        reject = _reject;
+    });
+
+    return {resolve, reject, promise};
+};