diff --git a/lib/externallib.php b/lib/externallib.php
index 4469d2abbde..eb7d1c96144 100644
--- a/lib/externallib.php
+++ b/lib/externallib.php
@@ -743,6 +743,7 @@ function external_format_string($str, $contextid, $striplinks = true, $options =
     if (!$settings->get_raw()) {
         $context = context::instance_by_id($contextid);
         $options['context'] = $context;
+        $options['filter'] = $settings->get_filter();
         $str = format_string($str, $striplinks, $options);
     }
 
diff --git a/lib/weblib.php b/lib/weblib.php
index 60b65d3bb49..634885bc1ff 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1354,6 +1354,9 @@ function format_string($string, $striplinks = true, $options = null) {
     } else if (is_numeric($options['context'])) {
         $options['context'] = context::instance_by_id($options['context']);
     }
+    if (!isset($options['filter'])) {
+        $options['filter'] = true;
+    }
 
     if (!$options['context']) {
         // We did not find any context? weird.
@@ -1372,7 +1375,7 @@ function format_string($string, $striplinks = true, $options = null) {
     // Regular expression moved to its own method for easier unit testing.
     $string = replace_ampersands_not_followed_by_entity($string);
 
-    if (!empty($CFG->filterall)) {
+    if (!empty($CFG->filterall) && $options['filter']) {
         $filtermanager = filter_manager::instance();
         $filtermanager->setup_page_for_filters($PAGE, $options['context']); // Setup global stuff filters may have.
         $string = $filtermanager->filter_string($string, $options['context']);