java.lang.String.replaceFirst from IBM VM throws NPE

We got problem with Harmony on IBM VM on Windows.
java.lang.String.replaceFirst throws NPE.

Here is the testcase:
public class Test {
    public static void main(String args[]) {
        String xx = "test";
        xx = xx.replaceFirst("t","z");
    }
}

Here is the stack trace:
C:\Work\Harmony\Sources\Harmony\deploy\jre\bin>java Test
Exception in thread "main" java.lang.NullPointerException
        at java.lang.String.replaceFirst(String.java:1642)
        at Test.main(Test.java:4)

Since IBM VM is not an OpenSource I can not check java.lang.String for
the cause of this problem :(

Can we ask IBM guys somehow to fix this issue?

--
Alexey A. Petrenko
Intel Middleware Products Division