Cannot use Web Service Tester to test GET requests returning 404

I get a NPE when I submit a GET request in the Web Service tester which should return 404. In Eclipse's .log file I only have these lines:
!ENTRY org.eclipse.core.jobs 4 2 2013-07-01 16:54:21.954
!MESSAGE An internal error occurred during: "Invoking web service...".
!STACK 0
java.lang.NullPointerException
at org.jboss.tools.ws.ui.views.JAXRSWSTestView2.handleRSTest(JAXRSWSTestView2.java:1918)
at org.jboss.tools.ws.ui.views.JAXRSWSTestView2.access$33(JAXRSWSTestView2.java:1916)
at org.jboss.tools.ws.ui.views.JAXRSWSTestView2$21.run(JAXRSWSTestView2.java:1723)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)