diff --git a/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Filter/ExtractStyleBlocks.php b/htdocs/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Filter/ExtractStyleBlocks.php
index 66f70b0fc0..7e1bfbac0a 100644
--- a/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Filter/ExtractStyleBlocks.php
+++ b/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Filter/ExtractStyleBlocks.php
@@ -121,6 +121,11 @@ class HTMLPurifier_Filter_ExtractStyleBlocks extends HTMLPurifier_Filter
      */
     public function cleanCSS($css, $config, $context)
     {
+        // Mahara customisation - allows CSS comments to not be stripped out
+        if ($config->get('Filter.ExtractStyleBlocks.PreserveCSS')) {
+            $this->_tidy->set_cfg('preserve_css_comment', true);
+        }
+
         // prepare scope
         $scope = $config->get('Filter.ExtractStyleBlocks.Scope');
         if ($scope !== null) {