--- a/testing/marionette/README
+++ b/testing/marionette/README
@@ -9,20 +9,20 @@ DESCRIPTION
   It can remotely control either the UI or the internal JavaScript of
   the Gecko platform, such as Firefox.  It can control both the chrome
   and the content document, giving a high level of control and ability to
   replicate user interaction.  In addition to performing actions on the
   browser, Marionette can also read properties and attributes of the DOM.
 
 USAGE
 
-  Marionette can be activated by passing the --marionette flag.  To start
+  Marionette can be activated by passing the -marionette flag.  To start
   Firefox with the remote protocol turned on:
 
-  	% firefox --marionette
+  	% firefox -marionette
   	…
   	1491228343089	Marionette	INFO	Listening on port 2828
 
   This binds to a TCP socket, over which CLIENTS can communicate with
   Marionette using the PROTOCOL.
 
 PROTOCOL
 

--- a/testing/marionette/components/marionette.js
+++ b/testing/marionette/components/marionette.js
@@ -149,17 +149,17 @@ MarionetteComponent.prototype.onSocketAc
   this.logger.info("onSocketAccepted for Marionette dummy socket");
 };
 
 MarionetteComponent.prototype.onStopListening = function (socket, status) {
   this.logger.info(`onStopListening for Marionette dummy socket, code ${status}`);
   socket.close();
 };
 
-// Handle --marionette flag
+// Handle -marionette flag
 MarionetteComponent.prototype.handle = function (cmdLine) {
   if (cmdLine.handleFlag("marionette", false)) {
     this.enabled = true;
   }
 };
 
 MarionetteComponent.prototype.observe = function (subject, topic, data) {
   switch (topic) {

--- a/testing/marionette/prefs/marionette.js
+++ b/testing/marionette/prefs/marionette.js
@@ -1,17 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // Marionette is the remote protocol that lets OOP programs communicate
 // with, instrument, and control Gecko.
 //
 // It is included in Firefox, but not enabled by default unless the
-// --marionette flag is passed.
+// -marionette flag is passed.
 
 // Port to start Marionette server on.
 pref("marionette.port", 2828);
 
 // Marionette logging verbosity.  Allowed values are "fatal", "error",
 // "warn", "info", "config", "debug", and "trace".
 pref("marionette.log.level", "info");