java.util.regex.Matcher does not respect the boundary specified by the method region(int, int) when matching against a supplementary character.

The following code is expected to print "false", but prints "true":
import java.util.regex.*;

public class T {
    public static void main(String[] args) throws Throwable {
        Pattern p = Pattern.compile("\\ud800\\udc61");
        Matcher m = p.matcher("\ud800\udc61");
        m.region(0, 1);
        System.out.println(m.find());
    }
}