Implicite Collections lead to duplicate id attribute in XML

Using a class with an implicite collection that has the same name as the class causes a doublicate id to be generated. Here is the test code:

public class Main {
public static void main(String[] args) {
final XStream x = new XStream(new DomDriver(new ClassPathEntityResolver("utf-8")));
x.setMode(XStream.ID_REFERENCES);
x.alias("strings", Strings.class);
x.addImplicitCollection(Strings.class, "strings");
final Strings m = new Strings(new String[]

);
System.out.println(x.toXML(m));
}
}

class Strings {
private ArrayList strings = new ArrayList();
public Strings(String[] strings)

}

Leads to:

<strings id="1" id="2">
<string>Hallo</string>
<string>Daniel</string>
</strings>

Cheers
Daniel