diff --git a/backup/moodle2/backup_xml_transformer.class.php b/backup/moodle2/backup_xml_transformer.class.php
index 63fb8a82bd38a..eb5b1766fa733 100644
--- a/backup/moodle2/backup_xml_transformer.class.php
+++ b/backup/moodle2/backup_xml_transformer.class.php
@@ -159,7 +159,7 @@ private function register_link_encoders() {
         // Add the module ones. Each module supporting moodle2 backups MUST have it
         $mods = core_component::get_plugin_list('mod');
         foreach ($mods as $mod => $moddir) {
-            if (plugin_supports('mod', $mod, FEATURE_BACKUP_MOODLE2)) {
+            if (plugin_supports('mod', $mod, FEATURE_BACKUP_MOODLE2) && class_exists('backup_' . $mod . '_activity_task')) {
                 $encoders['backup_' . $mod . '_activity_task'] = 'encode_content_links';
             }
         }