--- a/testing/marionette/client/marionette_driver/marionette.py
+++ b/testing/marionette/client/marionette_driver/marionette.py
@@ -586,16 +586,17 @@ class Marionette(object):
                     app = config.get('App', 'Name')
                     instance_class = geckoinstance.apps[app.lower()]
                 except (ConfigParser.NoOptionError,
                         ConfigParser.NoSectionError,
                         KeyError):
                     instance_class = geckoinstance.GeckoInstance
             self.instance = instance_class(host=self.host, port=self.port,
                                            bin=self.bin, profile=self.profile,
+                                           app_args=app_args,
                                            symbols_path=symbols_path,
                                            gecko_log=gecko_log, prefs=prefs,
                                            addons=self.addons,
                                            workspace=workspace,
                                            verbose=verbose)
             self.instance.start()
             self.raise_for_port(self.wait_for_port(timeout=startup_timeout))