A problem about proxies

I'm reading the chapter about proxies on Core Java 2
The book give a TraceHandler class as an example, which will print the
name of the method to be called.

import java.lang.reflect.*;

public class TraceHandler implements InvocationHandler {
    private Object target;

    public TraceHandler(Object t) {
        target = t;
    }

    public Object invoke(Object proxy, Method m, Object[] args) throws
Throwable {
        System.out.println("Method " + m + "invoked.");
        return m.invoke(target, args);
    }
}

I wrote a test interface and a class whichi implements it:
public interface MyInterface {
    int factorial(int n);
    void empty();
    void printSomething();
}

public class TargetObject implements MyInterface {
    public int factorial(int n) {
        return n <= 1 ? 0 : n * factorial(n - 1);
    }

    public void empty() {
    }

    public void printSomething() {
        System.out.println("Hello world as always");
    }
}

and a test class
import java.lang.reflect.*;

public class Test {
    public static void main(String[] args) {
        Object target = new TargetObject();
        InvocationHandler handler = new TraceHandler(target);
        Class[] interfaces = target.getClass().getInterfaces();
        Object proxy = Proxy.newProxyInstance(null, interfaces,
handler);
    }
}

But when i ran this Test program, it throws an exception
Exception in thread "main" java.lang.IllegalArgumentException:
interface MyInterface is not visible from class loader
        at java.lang.reflect.Proxy.getProxyClass(Proxy.java:353)
        at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:581)
        at Test.main(Test.java:9)

How to deal with this problem?

many thanks