--- a/testing/web-platform/harness/wptrunner/webdriver_server.py
+++ b/testing/web-platform/harness/wptrunner/webdriver_server.py
@@ -69,16 +69,19 @@ class WebDriverServer(object):
         self.logger.debug(
             "Waiting for server to become accessible: %s" % self.url)
         try:
             wait_for_service((self.host, self.port))
         except:
             self.logger.error(
                 "WebDriver HTTP server was not accessible "
                 "within the timeout:\n%s" % traceback.format_exc())
+            if self._proc.poll():
+                self.logger.error("Webdriver server process exited with code %i" %
+                                  self._proc.returncode)
             raise
 
         if block:
             self._proc.wait()
 
     def stop(self):
         if self.is_alive:
             return self._proc.kill()
@@ -145,18 +148,18 @@ class GeckoDriverServer(WebDriverServer)
         env["RUST_BACKTRACE"] = "1"
         WebDriverServer.__init__(self, logger, binary, host=host, port=port, env=env)
         self.marionette_port = marionette_port
 
     def make_command(self):
         return [self.binary,
                 "--connect-existing",
                 "--marionette-port", str(self.marionette_port),
-                "--webdriver-host", self.host,
-                "--webdriver-port", str(self.port)]
+                "--host", self.host,
+                "--port", str(self.port)]
 
 
 def cmd_arg(name, value=None):
     prefix = "-" if platform.system() == "Windows" else "--"
     rv = prefix + name
     if value is not None:
         rv += "=" + value
     return rv