WebMethod not being called

I’ve got a Page which contains many deeply nested Controls of various types.  Deep inside the hierarchy is an HtmlPanel.  The HTML source in that box contains an element:

<div class="blue" onclick="App.MainPage.popRule(-1,"...");">...</div>

The topmost page is indeed called MainPage:

using Wisej.Core;
using Wisej.Web;

namespace X
{
 public partial class MainPage : Page

and in that class there is a method:

 [WebMethod]
 public void popRule(string fileId, string targetPolicy, string targetType = "RULE")

But when the div is clicked, the method is not called.  While writing this out, I see that the method has a parameter with a default value, and re-factoring to eliminate the default-valued parameter fixes the problem.

So, what started out as a question becomes a suggestion:  make the default parameter work, or at least update the documentation to indicate that it’s not supported.