Index: lib/filterValidation.js
diff --git a/lib/filterValidation.js b/lib/filterValidation.js
index f5de14b7a75c670802a37fa676a10cb51c51dcd5..c280fcceba42d50b1b00ba55a1b5f0b091ba8a40 100644
--- a/lib/filterValidation.js
+++ b/lib/filterValidation.js
@@ -17,8 +17,10 @@
 
 /** @module filterValidation */
 
-let {Filter, InvalidFilter, ElemHideBase} = require("filterClasses");
-let {Utils} = require("utils");
+"use strict";
+
+const {Filter, InvalidFilter, ElemHideBase} = require("filterClasses");
+const {Utils} = require("utils");
 
 /**
  * An error returned by
@@ -63,7 +65,7 @@ FilterParsingError.prototype = {
    *
    * @return {string}
    */
-  toString: function()
+  toString()
   {
     let message;
     if (this.reason)
@@ -115,7 +117,7 @@ let parseFilter =
  * @param {string}  text
  * @return {ParsedFilter}
  */
-exports.parseFilter = function(text)
+exports.parseFilter = text =>
 {
   let filter = null;
   text = Filter.normalize(text);
@@ -149,7 +151,7 @@ exports.parseFilter = function(text)
  * @param {string}  text
  * @return {ParsedFilters}
  */
-exports.parseFilters = function(text)
+exports.parseFilters = text =>
 {
   let lines = text.split("\n");
   let filters = [];