diff --git a/src/@types/global.d.ts b/src/@types/global.d.ts
index ffd3277892..8486016cd0 100644
--- a/src/@types/global.d.ts
+++ b/src/@types/global.d.ts
@@ -20,6 +20,7 @@ import { IMatrixClientPeg } from "../MatrixClientPeg";
 import ToastStore from "../stores/ToastStore";
 import DeviceListener from "../DeviceListener";
 import { RoomListStore2 } from "../stores/room-list/RoomListStore2";
+import { PlatformPeg } from "../PlatformPeg";
 
 declare global {
     interface Window {
@@ -33,6 +34,7 @@ declare global {
         mx_ToastStore: ToastStore;
         mx_DeviceListener: DeviceListener;
         mx_RoomListStore2: RoomListStore2;
+        mxPlatformPeg: PlatformPeg;
     }
 
     // workaround for https://github.com/microsoft/TypeScript/issues/30933
diff --git a/src/PlatformPeg.js b/src/PlatformPeg.ts
similarity index 82%
rename from src/PlatformPeg.js
rename to src/PlatformPeg.ts
index 34131fde7d..42cb7acaf7 100644
--- a/src/PlatformPeg.js
+++ b/src/PlatformPeg.ts
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,6 +15,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import BasePlatform from "./BasePlatform";
+
 /*
  * Holds the current Platform object used by the code to do anything
  * specific to the platform we're running on (eg. web, electron)
@@ -21,10 +24,8 @@ limitations under the License.
  * This allows the app layer to set a Platform without necessarily
  * having to have a MatrixChat object
  */
-class PlatformPeg {
-    constructor() {
-        this.platform = null;
-    }
+export class PlatformPeg {
+    platform: BasePlatform = null;
 
     /**
      * Returns the current Platform object for the application.
@@ -44,7 +45,7 @@ class PlatformPeg {
     }
 }
 
-if (!global.mxPlatformPeg) {
-    global.mxPlatformPeg = new PlatformPeg();
+if (!window.mxPlatformPeg) {
+    window.mxPlatformPeg = new PlatformPeg();
 }
-export default global.mxPlatformPeg;
+export default window.mxPlatformPeg;