diff --git a/webxdc.d.ts b/webxdc.d.ts
index b2b03a3..c0330d7 100644
--- a/webxdc.d.ts
+++ b/webxdc.d.ts
@@ -40,7 +40,7 @@ interface Webxdc<T> {
    * The "serial" specifies the last serial that you know about (defaults to 0).
    * Note that own status updates, that you send with {@link sendUpdate}, also trigger this method
    * */
-  setUpdateListener(cb: (statusUpdate: ReceivedStatusUpdate<T>) => void, serial: number): void;
+  setUpdateListener(cb: (statusUpdate: ReceivedStatusUpdate<T>) => void, serial?: number): void;
   /**
    * WARNING! This function is deprecated, see setUpdateListener().
    */
diff --git a/webxdc.js b/webxdc.js
index 7c27cc4..23d483e 100644
--- a/webxdc.js
+++ b/webxdc.js
@@ -25,7 +25,7 @@ window.webxdc = (() => {
     return {
         selfAddr: params.get("addr") || "device0@local.host",
         selfName: params.get("name") || "device0",
-        setUpdateListener: (cb, serial) => {
+        setUpdateListener: (cb, serial = 0) => {
             var updates = getUpdates();
             var maxSerial = updates.length;
             updates.forEach((update) => {