Perfoming an action against the response that would cause an IllegalStateException if the response has been comitted

I'm trying to run tck/servlet test with jetty6.1.4. Some cases failed.

Below is the test strategy for one of the failed cases:
@test_Strategy: Validate PageContext.include() with flush argument provided

• and set to true. Response should be commited after the
• flush. Test validates this by perfoming an action against
• the response that would cause an IllegalStateException if
• the response has been comitted. This also validated
• the inclusion of a resource identified by a page-relative path

To simplify it, I had write a simple jsp file to reproduce this issue.

<%@ page import="java.io.PrintWriter"%>
<%@ page contentType="text/plain"%>

<%
boolean passed = false;
PrintWriter pw = response.getWriter();
pw.println("THIS TEXT SHOULD APPEAR");
response.flushBuffer();
try

{ response.sendError(1,"HttpServletResponse.SC_GONE"); passed = false; pw.println("IllegalStateException exception should have been thrown"); }

catch (Throwable t) {
if (t instanceof IllegalStateException)

{ passed = true; }

else

{ passed = false; pw.println("Exception thrown, but was not an instance of IllegalStateException."); pw.println("instead received: " + t.getClass().getName()); }

}
pw.println("Is test passed? "+passed);
%>

I had tested this jsp file with jetty6.1.3 and jetty6.1.4.

6.1.3 can work fine but 6.1.4 failed.