cannot parse extending an inner class when generics are involved

The following code:

ParentTree.java:
package org.example;

public class ParentTree<K, V> {

public class Node {

}
}

ChildTree.java:
package org.example;

public class ChildTree<K, V> extends ParentTree<K, V> {

protected class Node extends ParentTree<K,V>.Node {

}

}

fails to parse with the error:
ParseException in ...\src\java\org\example\ChildTree.java
Last useful checkpoint: "org.example.ChildTree.Node"
Encountered "." at line 5, column 48.
Was expecting one of:
"implements" ...
"{" ...
">>" ...
">>>" ...

While this code is not likely to be encountered much, it is valid java code compiled with javac (JDK6 in my case - though it should be valid Java 5 code as well).