ConcurrentSkipListMap.remove(null,null) will not throw NullPointerException but the spec says Throws NullPointerException if specified key is NULL

<testcase>
import java.util.concurrent.ConcurrentSkipListMap;
public class Test02 {
    public static void main(String[] args) {
        ConcurrentSkipListMap<Integer,Boolean> map =
                     new ConcurrentSkipListMap<Integer,Boolean>();
        try{
            map.remove(null,null);
            System.out.println("NullPointerException is not thrown");
        } catch(NullPointerException npe) {
            System.out.println("Yes ... NullPointerException");
        }
    }
}
</testcase>
output of the above testcase :
NullPointerException is not thrown

Tried in Solaris S10:
<java-version>
java version "1.6.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta-b59g)
Java HotSpot(TM) Client VM (build 1.6.0-beta-b59g, mixed mode)
</java-version>