Cache not updated

[snfuchs]

Seems to me that the cache is not updated, when newer files are available on the server.
To test, I wrote this little test:
public void testServerReturnsDocumentNewerThanCache() throws Exception {
server.enqueue(new MockResponse().setBody("A")
.addHeader("Last-Modified: " + formatDate(-4, TimeUnit.HOURS)));
server.enqueue(new MockResponse().setBody("B")
.addHeader("Last-Modified: " + formatDate(-2, TimeUnit.HOURS)));
server.play();

    URL url = server.getUrl("/");

    assertEquals("A", readAscii(url.openConnection()));
    assertEquals("B", readAscii(url.openConnection()));
}

It fails on the last assert. A is returned instead of B.