[Vala] Defining new virtual signal is possible, but overring it isn't.

[Tal Hadad <tal_hd hotmail com>]

When I try to:
public class A : GLib.Object {
  public virtual signal void func () {}
}


public class B : A {

  public override void func () {}

}

I get an error from Valac:
error: B.func: no suitable method found to override

I'm using Vala 0.16.1

I think that this is a critical bug in Vala, or my code is wrong?

Thanks,
Tal