diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index 37fd90ad..c3faf213 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -19,7 +19,7 @@ import {Room} from "./room/Room.js";
 import {ArchivedRoom} from "./room/ArchivedRoom.js";
 import {RoomStatus} from "./room/RoomStatus.js";
 import {Invite} from "./room/Invite.js";
-import {Pusher} from "./push/Pusher.js";
+import {Pusher} from "./push/Pusher";
 import { ObservableMap } from "../observable/index.js";
 import {User} from "./User.js";
 import {DeviceMessageHandler} from "./DeviceMessageHandler.js";
diff --git a/src/matrix/push/Pusher.js b/src/matrix/push/Pusher.js
deleted file mode 100644
index 99baeae6..00000000
--- a/src/matrix/push/Pusher.js
+++ /dev/null
@@ -1,50 +0,0 @@
-export class Pusher {
-    constructor(description) {
-        this._description = description;
-    }
-
-    static httpPusher(host, appId, pushkey, data) {
-        return new Pusher({
-            kind: "http",
-            append: true,   // as pushkeys are shared between multiple users on one origin
-            data: Object.assign({}, data, {url: host + "/_matrix/push/v1/notify"}),
-            pushkey,
-            app_id: appId,
-            app_display_name: "Hydrogen",
-            device_display_name: "Hydrogen",
-            lang: "en"
-        });
-    }
-
-    static createDefaultPayload(sessionId) {
-        return {session_id: sessionId};
-    }
-
-    async enable(hsApi, log) {
-        try {
-            log.set("endpoint", new URL(this._description.data.endpoint).host);
-        } catch {
-            log.set("endpoint", null);
-        }
-        await hsApi.setPusher(this._description, {log}).response();
-    }
-
-    async disable(hsApi, log) {
-        const deleteDescription = Object.assign({}, this._description, {kind: null});
-        await hsApi.setPusher(deleteDescription, {log}).response();
-    }
-
-    serialize() {
-        return this._description;
-    }
-
-    equals(pusher) {
-        if (this._description.app_id !== pusher._description.app_id) {
-            return false;
-        }
-        if (this._description.pushkey !== pusher._description.pushkey) {
-            return false;
-        }
-        return JSON.stringify(this._description.data) === JSON.stringify(pusher._description.data);
-    }
-}
diff --git a/src/matrix/push/Pusher.ts b/src/matrix/push/Pusher.ts
new file mode 100644
index 00000000..f9a35a2c
--- /dev/null
+++ b/src/matrix/push/Pusher.ts
@@ -0,0 +1,90 @@
+/*
+Copyright 2021 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.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import type {HomeServerApi} from "../net/HomeServerApi.js";
+import type {ILogItem} from "../../logging/types";
+
+export interface IPusherDescription {
+    kind: "http" | "email" | "null";
+    lang: string;
+    device_display_name: string;
+    app_display_name: string;
+    app_id: string;
+    pushkey: string;
+    data: IPusherData;
+    append?: boolean;
+    profile_tag?: string;
+}
+
+interface IPusherData {
+    format?: string;
+    url?: string;
+    // todo: where did this come from?
+    endpoint?: string;
+}
+
+export class Pusher {
+    private readonly _description: IPusherDescription;
+
+    constructor(description: IPusherDescription) {
+        this._description = description;
+    }
+
+    static httpPusher(host: string, appId: string, pushkey: string, data: IPusherData): Pusher {
+        return new Pusher({
+            kind: "http",
+            append: true,   // as pushkeys are shared between multiple users on one origin
+            data: Object.assign({}, data, {url: host + "/_matrix/push/v1/notify"}),
+            pushkey,
+            app_id: appId,
+            app_display_name: "Hydrogen",
+            device_display_name: "Hydrogen",
+            lang: "en"
+        });
+    }
+
+    static createDefaultPayload(sessionId: string): {session_id: string} {
+        return {session_id: sessionId};
+    }
+
+    async enable(hsApi: HomeServerApi, log: ILogItem): Promise<void> {
+        try {
+            log.set("endpoint", new URL(this._description.data.endpoint!).host);
+        } catch {
+            log.set("endpoint", null);
+        }
+        await hsApi.setPusher(this._description, {log}).response();
+    }
+
+    async disable(hsApi: HomeServerApi, log: ILogItem): Promise<void> {
+        const deleteDescription = Object.assign({}, this._description, {kind: null});
+        await hsApi.setPusher(deleteDescription, {log}).response();
+    }
+
+    serialize(): IPusherDescription {
+        return this._description;
+    }
+
+    equals(pusher): boolean {
+        if (this._description.app_id !== pusher._description.app_id) {
+            return false;
+        }
+        if (this._description.pushkey !== pusher._description.pushkey) {
+            return false;
+        }
+        return JSON.stringify(this._description.data) === JSON.stringify(pusher._description.data);
+    }
+}