diff --git a/extensions/firefox/bootstrap.js b/extensions/firefox/bootstrap.js
index 34af30605..9fc481993 100644
--- a/extensions/firefox/bootstrap.js
+++ b/extensions/firefox/bootstrap.js
@@ -20,11 +20,7 @@
 const RESOURCE_NAME = "pdf.js";
 const EXT_PREFIX = "extensions.uriloader@pdf.js";
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
 const Cm = Components.manager;
-const Cu = Components.utils;
-const Cr = Components.results;
 
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
diff --git a/extensions/firefox/chrome/content.js b/extensions/firefox/chrome/content.js
index f2cf00a67..44bc792af 100644
--- a/extensions/firefox/chrome/content.js
+++ b/extensions/firefox/chrome/content.js
@@ -19,11 +19,7 @@
 (function contentScriptClosure() {
   // we need to use closure here -- we are running in the global context
 
-  const Cc = Components.classes;
-  const Ci = Components.interfaces;
   const Cm = Components.manager;
-  const Cu = Components.utils;
-  const Cr = Components.results;
 
   ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
   ChromeUtils.import("resource://gre/modules/Services.jsm");
diff --git a/extensions/firefox/content/PdfJs-stub.jsm b/extensions/firefox/content/PdfJs-stub.jsm
index d7f005db5..cea1a6e1b 100644
--- a/extensions/firefox/content/PdfJs-stub.jsm
+++ b/extensions/firefox/content/PdfJs-stub.jsm
@@ -12,7 +12,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint max-len: ["error", 100] */
 
 "use strict";
 
diff --git a/extensions/firefox/content/PdfJs.jsm b/extensions/firefox/content/PdfJs.jsm
index 91ba106d1..cbde0b77e 100644
--- a/extensions/firefox/content/PdfJs.jsm
+++ b/extensions/firefox/content/PdfJs.jsm
@@ -17,11 +17,7 @@
 
 var EXPORTED_SYMBOLS = ["PdfJs"];
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-const Cr = Components.results;
 const Cm = Components.manager;
-const Cu = Components.utils;
 
 const PREF_PREFIX = "pdfjs";
 const PREF_DISABLED = PREF_PREFIX + ".disabled";
@@ -50,9 +46,9 @@ XPCOMUtils.defineLazyServiceGetter(Svc, "pluginHost",
                                    "@mozilla.org/plugin/host;1",
                                    "nsIPluginHost");
 ChromeUtils.defineModuleGetter(this, "PdfjsChromeUtils",
-                                  "resource://pdf.js/PdfjsChromeUtils.jsm");
+                               "resource://pdf.js/PdfjsChromeUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "PdfjsContentUtils",
-                                  "resource://pdf.js/PdfjsContentUtils.jsm");
+                               "resource://pdf.js/PdfjsContentUtils.jsm");
 
 function getBoolPref(aPref, aDefaultValue) {
   try {
diff --git a/extensions/firefox/content/PdfJsTelemetry.jsm b/extensions/firefox/content/PdfJsTelemetry.jsm
index f322177f5..4fc6efe76 100644
--- a/extensions/firefox/content/PdfJsTelemetry.jsm
+++ b/extensions/firefox/content/PdfJsTelemetry.jsm
@@ -18,7 +18,6 @@
 
 this.EXPORTED_SYMBOLS = ["PdfJsTelemetry"];
 
-const Cu = Components.utils;
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 this.PdfJsTelemetry = {
diff --git a/extensions/firefox/content/PdfStreamConverter.jsm b/extensions/firefox/content/PdfStreamConverter.jsm
index c1e77245b..a546dfb9c 100644
--- a/extensions/firefox/content/PdfStreamConverter.jsm
+++ b/extensions/firefox/content/PdfStreamConverter.jsm
@@ -17,11 +17,6 @@
 
 var EXPORTED_SYMBOLS = ["PdfStreamConverter"];
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-const Cr = Components.results;
-const Cu = Components.utils;
-
 const PDFJS_EVENT_ID = "pdf.js.message";
 const PREF_PREFIX = "PDFJSSCRIPT_PREF_PREFIX";
 const PDF_VIEWER_WEB_PAGE = "resource://pdf.js/web/viewer.html";
@@ -111,7 +106,7 @@ function getDOMWindow(aChannel) {
   var requestor = aChannel.notificationCallbacks ?
                   aChannel.notificationCallbacks :
                   aChannel.loadGroup.notificationCallbacks;
-  var win = requestor.getInterface(Components.interfaces.nsIDOMWindow);
+  var win = requestor.getInterface(Ci.nsIDOMWindow);
   return win;
 }
 
diff --git a/extensions/firefox/content/PdfjsChromeUtils.jsm b/extensions/firefox/content/PdfjsChromeUtils.jsm
index c4428e0f4..5ef9c6a37 100644
--- a/extensions/firefox/content/PdfjsChromeUtils.jsm
+++ b/extensions/firefox/content/PdfjsChromeUtils.jsm
@@ -17,11 +17,6 @@
 
 var EXPORTED_SYMBOLS = ["PdfjsChromeUtils"];
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-const Cr = Components.results;
-const Cu = Components.utils;
-
 const PREF_PREFIX = "PDFJSSCRIPT_PREF_PREFIX";
 const PDF_CONTENT_TYPE = "application/pdf";
 
diff --git a/extensions/firefox/content/PdfjsContentUtils.jsm b/extensions/firefox/content/PdfjsContentUtils.jsm
index 1c39cc9d7..3f6f336a6 100644
--- a/extensions/firefox/content/PdfjsContentUtils.jsm
+++ b/extensions/firefox/content/PdfjsContentUtils.jsm
@@ -17,12 +17,6 @@
 
 var EXPORTED_SYMBOLS = ["PdfjsContentUtils"];
 
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-const Cr = Components.results;
-const Cu = Components.utils;
-
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 var PdfjsContentUtils = {
diff --git a/extensions/firefox/tools/l10n.js b/extensions/firefox/tools/l10n.js
index 35bdbe457..74cce0104 100644
--- a/extensions/firefox/tools/l10n.js
+++ b/extensions/firefox/tools/l10n.js
@@ -112,7 +112,7 @@
       // use the short language code for "full" codes like 'ar-sa' (issue 5440)
       var shortCode = gLanguage.split("-")[0];
 
-      return (rtlList.indexOf(shortCode) >= 0) ? "rtl" : "ltr";
+      return (rtlList.includes(shortCode) ? "rtl" : "ltr");
     },
 
     getReadyState() {
diff --git a/package.json b/package.json
index f808c4a57..9705fe184 100644
--- a/package.json
+++ b/package.json
@@ -9,8 +9,8 @@
     "babel-preset-env": "^1.6.1",
     "core-js": "^2.5.3",
     "escodegen": "^1.9.0",
-    "eslint": "^4.16.0",
-    "eslint-plugin-mozilla": "^0.7.0",
+    "eslint": "^4.17.0",
+    "eslint-plugin-mozilla": "^0.8.1",
     "eslint-plugin-no-unsanitized": "^2.0.2",
     "fancy-log": "^1.3.2",
     "gulp": "^3.9.1",