Sanity check, just verify that there aren't any other cases in lib/classes/message/manager.php pointing to global-scope code and missing the backslash. For reference, I've done that here, getting the results below, and ALL the potential cases are effectively using a correct namespace or global \. $ ag -s ' new |(?<!self)::' lib/classes/message/manager.php 71: throw new \moodle_exception("Message is not being sent to a conversation. Please check event data."); 95: $members = $DB->get_records_sql($sql, [$eventdata->convid, \core_message\api::CONVERSATION_ACTION_MUTED, 98: throw new \moodle_exception("Conversation has no members or does not exist."); 114: if ($conv->type == \core_message\api::MESSAGE_CONVERSATION_TYPE_SELF) { 124: if ($conv->type == \core_message\api::MESSAGE_CONVERSATION_TYPE_INDIVIDUAL) { 157: $usertoisrealuser = (\core_user::is_real_user($recipient->id) != false); 161: if ($conv->type == \core_message\api::MESSAGE_CONVERSATION_TYPE_INDIVIDUAL) { 164: } else if ($conv->type == \core_message\api::MESSAGE_CONVERSATION_TYPE_GROUP) { 181: $s = new \stdClass(); 182: $s->sitename = format_string($SITE->shortname, true, array('context' => \context_course::instance(SITEID))); 191: \core_message\helper::prevent_unclosed_html_tags($localisedeventdata->fullmessage, true); 199: \core_message\helper::prevent_unclosed_html_tags($localisedeventdata->fullmessagehtml, true); 244: throw new \coding_exception($preferrormsg); 346: \core_message\api::mark_notification_as_read($savemessage); 349: \core_message\api::mark_message_as_read($eventdata->userto->id, $savemessage); 395: \core_message\api::mark_message_as_read($eventdata->userto->id, $savemessage); 454: \core\event\notification_sent::create_from_ids( 464: if ($conv->type == \core_message\api::MESSAGE_CONVERSATION_TYPE_GROUP) { 465: \core\event\group_message_sent::create_from_ids( 475: \core\event\message_sent::create_from_ids( 495: // Let new messaging class add custom content based on the processor. 506: $stdproc = new \stdClass(); 508: $processor = \core_message\api::get_processed_processor_object($stdproc);