diff --git a/testing/marionette/error.js b/testing/marionette/error.js
index 5a3b4c14572e..0eb58986bf1c 100644
--- a/testing/marionette/error.js
+++ b/testing/marionette/error.js
@@ -196,7 +196,6 @@ this.InvalidSessionIdError = function(msg) {
   WebDriverError.call(this, msg);
   this.name = "InvalidSessionIdError";
   this.status = "invalid session id";
-  this.code = 13;
 };
 InvalidSessionIdError.prototype = Object.create(WebDriverError.prototype);
 
@@ -307,7 +306,6 @@ this.UnableToSetCookieError = function(msg) {
   WebDriverError.call(this, msg);
   this.name = "UnableToSetCookieError";
   this.status = "unable to set cookie";
-  this.code = 25;
 };
 UnableToSetCookieError.prototype = Object.create(WebDriverError.prototype);