diff --git a/erpnext/crm/doctype/appointment/appointment.py b/erpnext/crm/doctype/appointment/appointment.py
index b6962d923a..2affba2ac4 100644
--- a/erpnext/crm/doctype/appointment/appointment.py
+++ b/erpnext/crm/doctype/appointment/appointment.py
@@ -28,8 +28,9 @@ class Appointment(Document):
 		number_of_appointments_in_same_slot = frappe.db.count(
 			'Appointment', filters={'scheduled_time': self.scheduled_time})
 		number_of_agents = frappe.db.get_single_value('Appointment Booking Settings', 'number_of_agents')
-		if (number_of_appointments_in_same_slot >= number_of_agents):
-			frappe.throw('Time slot is not available')
+		if not number_of_agents == 0:
+			if (number_of_appointments_in_same_slot >= number_of_agents):
+				frappe.throw('Time slot is not available')
 		# Link lead
 		if not self.lead:
 			self.lead = self.find_lead_by_email()