BookmarkablePageLink cannot correctly pass PageParameters with Chinese characters.

I have a form , after submitting that form , it will embed some paramaters and redirect to some page :

public void onSubmit()
{
PageParameters pps = new PageParameters();
pps.put("place", "台北市"); // "台北市" is Chinese characters : "Taipei"
setResponsePage(FirstPage.class , pps);
}

When directed to FirstPage.java , the URL correctly shows "/place/台北市"
and I can use URLDecoder to get correct place = "台北市" :
place = URLDecoder.decode(pps.getString("place") , "UTF-8");

Everything seems works fine here...
But things get complicated after adding a NavigationPanel to the FirstPage :

public class LeftNavigationPanel extends Panel
{
public LeftNavigationPanel(String id , final PageParameters pps)

}

I want the SecondPage appends whatever appended in the FirstPage , so I pass PageParameters to it.

Here comes the problem :
In the SecondPage , parameter "place" is not "台北市" any more ,
it becomes :
%25E5%258F%25B0%25E5%258C%2597%25E5%25B8%2582

I feel it is a bug regarding to BookmarkablePageLink.
Can you confirm / fix it ?