--- a/mail/test/mozmill/runtest.py
+++ b/mail/test/mozmill/runtest.py
@@ -221,17 +221,17 @@ class ThunderTestRunner(mozrunner.Thunde
         the keyboard interrupt case wait will die due to the interrupt and
         stop/kill will be killed.  Since we are wrapping wait, we don't need
         to specialize for stop/kill though.
         '''
         try:
             return mozrunner.ThunderbirdRunner.wait(self, timeout)
         finally:
             try:
-                if self.vnc_alive:
+                if self.use_vnc_server and self.vnc_alive:
                     subprocess.check_call([self.VNC_SERVER_PATH,
                                            '-kill', ':99'])
             except Exception, ex:
                 print '!!! Exception during killing VNC server:', ex
 
 
 class ThunderTestCLI(mozmill.CLI):