PageMethods undefined error when WebMethod is within Server Control

I have a server control I'm building with ASP.NET AJAX, and I'm trying to make it expose WebMethods. When I put the WebMethods in the .aspx page everything works fine, but when I put the WebMethods inside the custom server control itself I get an error.

Is it possible to expose WebMethods from within a custom Server Control or UserControl? If so, How? If not, Why not?

Thanks
...