diff --git a/lib/tests/weblib_test.php b/lib/tests/weblib_test.php
index 513ee7b43ba..460d7e45980 100644
--- a/lib/tests/weblib_test.php
+++ b/lib/tests/weblib_test.php
@@ -567,4 +567,19 @@ EXPECTED;
         $this->assertSame($expected, strip_pluginfile_content($source));
     }
 
+    public function test_purify_html_ruby() {
+
+        $this->resetAfterTest();
+
+        $ruby =
+            "<p><ruby><rb>京都</rb><rp>(</rp><rt>きょうと</rt><rp>)</rp></ruby>は" .
+            "<ruby><rb>日本</rb><rp>(</rp><rt>にほん</rt><rp>)</rp></ruby>の" .
+            "<ruby><rb>都</rb><rp>(</rp><rt>みやこ</rt><rp>)</rp></ruby>です。</p>";
+        $illegal = '<script src="//code.jquery.com/jquery-1.11.3.min.js"></script>';
+
+        $cleaned = purify_html($ruby . $illegal);
+        $this->assertEquals($ruby, $cleaned);
+
+    }
+
 }
diff --git a/lib/weblib.php b/lib/weblib.php
index bd3689b3313..bb671da80c0 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1705,7 +1705,7 @@ function purify_html($text, $options = array()) {
         $config = HTMLPurifier_Config::createDefault();
 
         $config->set('HTML.DefinitionID', 'moodlehtml');
-        $config->set('HTML.DefinitionRev', 2);
+        $config->set('HTML.DefinitionRev', 3);
         $config->set('Cache.SerializerPath', $cachedir);
         $config->set('Cache.SerializerPermissions', $CFG->directorypermissions);
         $config->set('Core.NormalizeNewlines', false);
@@ -1744,6 +1744,9 @@ function purify_html($text, $options = array()) {
             $def->addElement('algebra', 'Inline', 'Inline', array());                   // Algebra syntax, equivalent to @@xx@@.
             $def->addElement('lang', 'Block', 'Flow', array(), array('lang'=>'CDATA')); // Original multilang style - only our hacked lang attribute.
             $def->addAttribute('span', 'xxxlang', 'CDATA');                             // Current very problematic multilang.
+
+            // Use the built-in Ruby module to add annotation support.
+            $def->manager->addModule(new HTMLPurifier_HTMLModule_Ruby());
         }
 
         $purifier = new HTMLPurifier($config);