--- a/testing/mochitest/runtestsb2g.py
+++ b/testing/mochitest/runtestsb2g.py
@@ -130,17 +130,20 @@ class B2GMochitest(MochitestUtilsMixin):
             runner_args = { 'profile': self.profile,
                             'devicemanager': self._dm,
                             'marionette': self.marionette,
                             'remote_test_root': self.remote_test_root,
                             'test_script': self.test_script,
                             'test_script_args': self.test_script_args }
             self.runner = B2GRunner(**runner_args)
             self.runner.start(outputTimeout=timeout)
-            self.runner.wait()
+            status = self.runner.wait()
+            if status is None:
+                # the runner has timed out
+                status = 124
         except KeyboardInterrupt:
             log.info("runtests.py | Received keyboard interrupt.\n");
             status = -1
         except:
             traceback.print_exc()
             log.error("Automation Error: Received unexpected exception while running application\n")
             status = 1