diff --git a/mocha.js b/mocha.js
index 1cd099076f..2135a9554a 100644
--- a/mocha.js
+++ b/mocha.js
@@ -5990,7 +5990,7 @@ mocha.run = function(fn){
 
   return Mocha.prototype.run.call(mocha, function(err){
     // The DOM Document is not available in Web Workers.
-    if (global.document && options.noHighlighting !== false) {
+    if (global.document && options.noHighlighting !== true) {
       Mocha.utils.highlightTags('code');
     }
     if (fn) fn(err);
diff --git a/support/tail.js b/support/tail.js
index 1abea5def9..5635fa5f59 100644
--- a/support/tail.js
+++ b/support/tail.js
@@ -144,7 +144,7 @@ mocha.run = function(fn){
 
   return Mocha.prototype.run.call(mocha, function(err){
     // The DOM Document is not available in Web Workers.
-    if (global.document && options.noHighlighting !== false) {
+    if (global.document && options.noHighlighting !== true) {
       Mocha.utils.highlightTags('code');
     }
     if (fn) fn(err);