diff --git a/erpnext/crm/doctype/appointment/appointment.py b/erpnext/crm/doctype/appointment/appointment.py
index 219f931..b259758 100644
--- a/erpnext/crm/doctype/appointment/appointment.py
+++ b/erpnext/crm/doctype/appointment/appointment.py
@@ -47,7 +47,7 @@
 							subject=_('Appointment Confirmation'))
 			frappe.msgprint('Please check your email to confirm the appointment')
 
-	def on_update():
+	def on_update(self):
 		# Sync Calednar
 		cal_event = frappe.get_doc('Event',self.calendar_event)
 		cal_event.starts_on = self.scheduled_time