diff --git a/mod/book/tool/print/lib.php b/mod/book/tool/print/lib.php
index eecdb7bb89e..81b33f6c522 100644
--- a/mod/book/tool/print/lib.php
+++ b/mod/book/tool/print/lib.php
@@ -22,8 +22,6 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
-defined('MOODLE_INTERNAL') || die;
-
 /**
  * Adds module specific settings to the settings block
  *
@@ -31,21 +29,45 @@ defined('MOODLE_INTERNAL') || die;
  * @param navigation_node $node The node to add module settings to
  */
 function booktool_print_extend_settings_navigation(settings_navigation $settings, navigation_node $node) {
+    global $OUTPUT;
+
     $params = $settings->get_page()->url->params();
-    if (empty($params['id']) or empty($params['chapterid'])) {
+    if (empty($params['id']) || empty($params['chapterid'])) {
         return;
     }
 
     if (has_capability('booktool/print:print', $settings->get_page()->cm->context)) {
-        $url1 = new moodle_url('/mod/book/tool/print/index.php', array('id'=>$params['id']));
-        $url2 = new moodle_url('/mod/book/tool/print/index.php', array('id'=>$params['id'], 'chapterid'=>$params['chapterid']));
+        $url1 = new moodle_url('/mod/book/tool/print/index.php', ['id' => $params['id']]);
+        $url2 = new moodle_url('/mod/book/tool/print/index.php', ['id' => $params['id'], 'chapterid' => $params['chapterid']]);
         $action = new action_link($url1, get_string('printbook', 'booktool_print'), new popup_action('click', $url1));
-        $booknode = $node->add(get_string('printbook', 'booktool_print'), $action, navigation_node::TYPE_SETTING, null, 'printbook',
-                new pix_icon('book', '', 'booktool_print', array('class' => 'icon')));
+        $newwindowtext = html_writer::span(' (' . get_string('opensinnewwindow') . ')', 'visually-hidden');
+        $externalicon = $OUTPUT->pix_icon('i/externallink', '', attributes: [
+            'title' => get_string('opensinnewwindow'),
+            'class' => 'ms-1',
+        ]);
+
+        $booknode = $node->add(
+            // Add both an icon and visualy hidden text to indicate link opens in a new window
+            // because Clean theme strips out the icon html.
+            get_string('printbook', 'booktool_print') . $externalicon . $newwindowtext,
+            $action,
+            navigation_node::TYPE_SETTING,
+            null,
+            'printbook',
+            new pix_icon('book', '', 'booktool_print', ['class' => 'icon'])
+        );
         $booknode->set_force_into_more_menu(true);
         $action = new action_link($url2, get_string('printchapter', 'booktool_print'), new popup_action('click', $url2));
-        $chapternode = $node->add(get_string('printchapter', 'booktool_print'), $action, navigation_node::TYPE_SETTING, null,
-            'printchapter', new pix_icon('chapter', '', 'booktool_print', array('class' => 'icon')));
+        $chapternode = $node->add(
+            // Add both an icon and visualy hidden text to indicate link opens in a new window
+            // because Clean theme strips out the icon html.
+            get_string('printchapter', 'booktool_print') . $externalicon . $newwindowtext,
+            $action,
+            navigation_node::TYPE_SETTING,
+            null,
+            'printchapter',
+            new pix_icon('chapter', '', 'booktool_print', ['class' => 'icon'])
+        );
         $chapternode->set_force_into_more_menu(true);
     }
 }
@@ -60,5 +82,5 @@ function booktool_print_extend_settings_navigation(settings_navigation $settings
  * @return array
  */
 function booktool_print_get_view_actions() {
-    return array('print');
+    return ['print'];
 }