diff --git a/Gruntfile.js b/Gruntfile.js
index 623bf429..81dd4540 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -276,7 +276,9 @@ module.exports = function (grunt) {
         reset: true,
         relaxerror: [
           'Bad value X-UA-Compatible for attribute http-equiv on element meta.',
-          'Element img is missing required attribute src.'
+          'Element img is missing required attribute src.',
+          'This interface to HTML5 document checking is deprecated.',
+          '\\& did not start a character reference. \\(\\& probably should have been escaped as \\&.\\)'
         ]
       },
       files: {