Query on usage of 'Window()' default constructor in java

I had been through this query before asking this question.

In class Window we have constructor with default direct access level package private but not private as shown below:

Window() throws HeadlessException {
        GraphicsEnvironment.checkHeadless();
        init((GraphicsConfiguration)null);
    }

With class dummy inheriting class Window,

import java.awt.*;

public class dummy extends Window{
    dummy() {

    }
}

I see this error: Implicit super constructor Window() is not visible. Must explicitly invoke another constructor

I designed non-public class with zero-arg constructor having default direct access level package private and the subclass constructor invokes zero-arg Superclass constructor without any error.

I would like to understand,

Why does the compiler show this error despite the direct access level to the constructor Window(){} is package private?

Note: I am using jdk 1.6