JUnit test for System.out.println()

I need to write JUnit tests for an old application that's poorly designed and is writing a lot of error messages to standard output. When the getResponse(String request) method behaves correctly it returns a XML response:

@BeforeClass
public static void setUpClass() throws Exception {
    Properties queries = loadPropertiesFile("requests.properties");
    Properties responses = loadPropertiesFile("responses.properties");
    instance = new ResponseGenerator(queries, responses);
}

@Test
public void testGetResponse() {
    String request = "request";
    String expResult = "response";
    String result = instance.getResponse(request);
    assertEquals(expResult, result);
}

But when it gets malformed XML or does not understand the request it returns null and writes some stuff to standard output.

Is there any way to assert console output in JUnit? To catch cases like:

System.out.println("match found: " + strExpr);
System.out.println("xml not well formed: " + e.getMessage());