diff --git a/erpnext/maintenance/doctype/maintenance_schedule/maintenance_schedule.py b/erpnext/maintenance/doctype/maintenance_schedule/maintenance_schedule.py
index 2ffae1a4f2a9..f4532f5231d8 100644
--- a/erpnext/maintenance/doctype/maintenance_schedule/maintenance_schedule.py
+++ b/erpnext/maintenance/doctype/maintenance_schedule/maintenance_schedule.py
@@ -1,6 +1,7 @@
 # Copyright (c) 2015, Frappe Technologies Pvt. Ltd. and Contributors
 # License: GNU General Public License v3. See license.txt
 
+import json
 
 import frappe
 from frappe import _, throw
@@ -306,13 +307,27 @@ def get_pending_data(self, data_type, s_date=None, item_name=None):
 					return schedule.name
 
 @frappe.whitelist()
-def update_serial_nos(s_id):
-	serial_nos = frappe.db.get_value('Maintenance Schedule Detail', s_id, 'serial_no')
+def update_serial_nos(s_id, item):
+	if isinstance(item, str):
+		item = json.loads(item)
+		item = frappe._dict(item)
+
+	serial_nos = []
+	if s_id:
+		serial_nos = frappe.db.get_value('Maintenance Schedule Detail', s_id, 'serial_no')
+
+	# for old docs which were already saved.
+	elif item.get('prevdoc_docname'):
+		serial_nos = frappe.db.get_value('Maintenance Schedule Item', {
+			'parent': item.prevdoc_docname,
+			'item_code': item.item_code
+		}, 'serial_no')
+
 	if serial_nos:
 		serial_nos = get_serial_nos(serial_nos)
 		return serial_nos
-	else:
-		return False
+
+	return []
 
 @frappe.whitelist()
 def make_maintenance_visit(source_name, target_doc=None, item_name=None, s_id=None):
diff --git a/erpnext/maintenance/doctype/maintenance_visit/maintenance_visit.js b/erpnext/maintenance/doctype/maintenance_visit/maintenance_visit.js
index 7f983541f6dc..60a8a02da1cd 100644
--- a/erpnext/maintenance/doctype/maintenance_visit/maintenance_visit.js
+++ b/erpnext/maintenance/doctype/maintenance_visit/maintenance_visit.js
@@ -2,45 +2,41 @@
 // License: GNU General Public License v3. See license.txt
 
 frappe.provide("erpnext.maintenance");
-var serial_nos = [];
 frappe.ui.form.on('Maintenance Visit', {
-	refresh: function (frm) {
-		//filters for serial_no based on item_code
-		frm.set_query('serial_no', 'purposes', function (frm, cdt, cdn) {
-			let item = locals[cdt][cdn];
-			if (serial_nos) {
-				return {
-					filters: {
-						'item_code': item.item_code,
-						'name': ["in", serial_nos]
-					}
-				};
-			} else {
-				return {
-					filters: {
-						'item_code': item.item_code
-					}
-				};
-			}
-		});
-	},
 	setup: function (frm) {
 		frm.set_query('contact_person', erpnext.queries.contact_query);
 		frm.set_query('customer_address', erpnext.queries.address_query);
 		frm.set_query('customer', erpnext.queries.customer);
 	},
 	onload: function (frm, cdt, cdn) {
-		let item = locals[cdt][cdn];
+		// filters for serial no based on item code
 		if (frm.doc.maintenance_type === "Scheduled") {
-			const schedule_id = item.purposes[0].prevdoc_detail_docname || frm.doc.maintenance_schedule_detail;
+			const schedule_id = frm.doc.maintenance_schedule_detail;
+			let item = frm.doc.purposes[0];
 			frappe.call({
 				method: "erpnext.maintenance.doctype.maintenance_schedule.maintenance_schedule.update_serial_nos",
 				args: {
-					s_id: schedule_id
-				},
-				callback: function (r) {
-					serial_nos = r.message;
+					s_id: schedule_id,
+					item: item
 				}
+			}).then((r) => {
+				let serial_nos = r.message;
+				frm.set_query('serial_no', 'purposes', function () {
+					if (serial_nos.length > 0) {
+						return {
+							filters: {
+								'item_code': item.item_code,
+								'name': ["in", serial_nos]
+							}
+						};
+					}
+					return {
+						filters: {
+							'item_code': item.item_code
+						}
+					};
+				});
+
 			});
 		}
 		else {
@@ -63,7 +59,6 @@ frappe.ui.form.on('Maintenance Visit', {
 	contact_person: function (frm) {
 		erpnext.utils.get_contact_details(frm);
 	}
-
 })
 
 // TODO commonify this code