diff --git a/filter/multilang/lang/en/filter_multilang.php b/filter/multilang/lang/en/filter_multilang.php
index 45018e7aa0a..3292b5dd206 100644
--- a/filter/multilang/lang/en/filter_multilang.php
+++ b/filter/multilang/lang/en/filter_multilang.php
@@ -24,4 +24,6 @@
  */
 
 $string['filtername'] = 'Multi-Language Content';
+$string['forceoldsyntax'] = 'Force old syntax';
+$string['forceoldsyntax_desc'] = 'Force old multilang syntax: <span> without the class="multilang" and <lang>';
 $string['privacy:metadata'] = 'The Multi-Language Content plugin does not store any personal data.';
diff --git a/filter/multilang/settings.php b/filter/multilang/settings.php
index a407911db71..de000096906 100644
--- a/filter/multilang/settings.php
+++ b/filter/multilang/settings.php
@@ -4,6 +4,10 @@ defined('MOODLE_INTERNAL') || die;
 
 if ($ADMIN->fulltree) {
 
-    $settings->add(new admin_setting_configcheckbox('filter_multilang_force_old', 'filter_multilang_force_old',
-                       get_string('multilangforceold', 'admin'), 0));
+    $settings->add(new admin_setting_configcheckbox(
+        'filter_multilang_force_old',
+        get_string('forceoldsyntax', 'filter_multilang'),
+        get_string('forceoldsyntax_desc', 'filter_multilang'),
+        0
+    ));
 }
diff --git a/lang/en/admin.php b/lang/en/admin.php
index efd4a1b0fc9..bcae00dd762 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -861,7 +861,6 @@ $string['mobilenotconfiguredwarning'] = 'The Moodle app is not enabled.';
 $string['modeditdefaults'] = 'Default values for activity settings';
 $string['modsettings'] = 'Manage activities';
 $string['modulesecurity'] = 'Module security';
-$string['multilangforceold'] = 'Force old multilang syntax: <span> without the class="multilang" and <lang>';
 $string['mustenablestats'] = 'Statistics have not yet been enabled on this site.';
 $string['mycourses'] = 'My courses';
 $string['mycoursesperpage'] = 'Number of courses';
@@ -1563,3 +1562,6 @@ $string['modchooserdefault'] = 'Activity chooser default';
 $string['coursepage'] = 'Course page';
 $string['mediapluginswf'] = 'Enable .swf filter';
 $string['mediapluginswfnote'] = 'As a default security measure, normal users should not be allowed to embed swf flash files.';
+
+// Deprecated since Moodle 4.1.
+$string['multilangforceold'] = 'Force old multilang syntax: <span> without the class="multilang" and <lang>';
diff --git a/lang/en/deprecated.txt b/lang/en/deprecated.txt
index d8bbc611aa8..8be37e81035 100644
--- a/lang/en/deprecated.txt
+++ b/lang/en/deprecated.txt
@@ -81,3 +81,4 @@ sendingviawhen,core_message
 close,core_contentbank
 notflagged,core_question
 cannotswitcheditmodeon,core_error
+multilangforceold,core_admin