Will make a new PR later

Author: ylesaout

src/index.js

@@ -329,7 +329,7 @@ const connectCallReceiver = (info, methods, destructionPromise) => {
  * for the child to respond before rejecting the connection promise.
  * @return {Child}
  */
-Penpal.connectToChild = ({ url, id = null, appendTo, methods = {}, timeout }) => {
+Penpal.connectToChild = ({ url, id, appendTo, methods = {}, timeout }) => {
   let destroy;
   const connectionDestructionPromise = new DestructionPromise(
     resolveConnectionDestructionPromise => {
@@ -339,7 +339,7 @@ Penpal.connectToChild = ({ url, id = null, appendTo, methods = {}, timeout }) =>
 
   const parent = window;
   const iframe = document.createElement('iframe');
-  iframe.id = id; 
+  (id !== undefined ? iframe.id = id : null); 
 
   (appendTo || document.body).appendChild(iframe);