diff --git a/erpnext/manufacturing/doctype/job_card/job_card.py b/erpnext/manufacturing/doctype/job_card/job_card.py
index 3bf9de2..ceae63c 100644
--- a/erpnext/manufacturing/doctype/job_card/job_card.py
+++ b/erpnext/manufacturing/doctype/job_card/job_card.py
@@ -91,7 +91,7 @@
 		if args.get("employee"):
 			# override capacity for employee
 			production_capacity = 1
-			validate_overlap_for = " and jc.employee = %(employee)s "
+			validate_overlap_for = " and jctl.employee = %(employee)s "
 
 		extra_cond = ''
 		if check_next_available_slot:
diff --git a/erpnext/manufacturing/doctype/job_card/test_job_card.py b/erpnext/manufacturing/doctype/job_card/test_job_card.py
index db0e08f..80295bb 100644
--- a/erpnext/manufacturing/doctype/job_card/test_job_card.py
+++ b/erpnext/manufacturing/doctype/job_card/test_job_card.py
@@ -8,71 +8,91 @@
 import frappe
 from frappe.utils import random_string
 
-from erpnext.manufacturing.doctype.job_card.job_card import OperationMismatchError
+from erpnext.manufacturing.doctype.job_card.job_card import OperationMismatchError, OverlapError
 from erpnext.manufacturing.doctype.work_order.test_work_order import make_wo_order_test_record
 from erpnext.manufacturing.doctype.workstation.test_workstation import make_workstation
 
 
 class TestJobCard(unittest.TestCase):
+
+	def setUp(self):
+		self.work_order = make_wo_order_test_record(item="_Test FG Item 2", qty=2)
+
+	def tearDown(self):
+		frappe.db.rollback()
+
 	def test_job_card(self):
-		data = frappe.get_cached_value('BOM',
-			{'docstatus': 1, 'with_operations': 1, 'company': '_Test Company'}, ['name', 'item'])
 
-		if data:
-			bom, bom_item = data
+		job_cards = frappe.get_all('Job Card',
+			filters = {'work_order': self.work_order.name}, fields = ["operation_id", "name"])
 
-			work_order = make_wo_order_test_record(item=bom_item, qty=1, bom_no=bom)
+		if job_cards:
+			job_card = job_cards[0]
+			frappe.db.set_value("Job Card", job_card.name, "operation_row_number", job_card.operation_id)
 
-			job_cards = frappe.get_all('Job Card',
-				filters = {'work_order': work_order.name}, fields = ["operation_id", "name"])
+			doc = frappe.get_doc("Job Card", job_card.name)
+			doc.operation_id = "Test Data"
+			self.assertRaises(OperationMismatchError, doc.save)
 
-			if job_cards:
-				job_card = job_cards[0]
-				frappe.db.set_value("Job Card", job_card.name, "operation_row_number", job_card.operation_id)
-
-				doc = frappe.get_doc("Job Card", job_card.name)
-				doc.operation_id = "Test Data"
-				self.assertRaises(OperationMismatchError, doc.save)
-
-			for d in job_cards:
-				frappe.delete_doc("Job Card", d.name)
+		for d in job_cards:
+			frappe.delete_doc("Job Card", d.name)
 
 	def test_job_card_with_different_work_station(self):
-		data = frappe.get_cached_value('BOM',
-			{'docstatus': 1, 'with_operations': 1, 'company': '_Test Company'}, ['name', 'item'])
+		job_cards = frappe.get_all('Job Card',
+			filters = {'work_order': self.work_order.name},
+			fields = ["operation_id", "workstation", "name", "for_quantity"])
 
-		if data:
-			bom, bom_item = data
+		job_card = job_cards[0]
 
-			work_order = make_wo_order_test_record(item=bom_item, qty=1, bom_no=bom)
+		if job_card:
+			workstation = frappe.db.get_value("Workstation",
+				{"name": ("not in", [job_card.workstation])}, "name")
 
-			job_cards = frappe.get_all('Job Card',
-				filters = {'work_order': work_order.name},
-				fields = ["operation_id", "workstation", "name", "for_quantity"])
+			if not workstation or job_card.workstation == workstation:
+				workstation = make_workstation(workstation_name=random_string(5)).name
 
-			job_card = job_cards[0]
+			doc = frappe.get_doc("Job Card", job_card.name)
+			doc.workstation = workstation
+			doc.append("time_logs", {
+				"from_time": "2009-01-01 12:06:25",
+				"to_time": "2009-01-01 12:37:25",
+				"time_in_mins": "31.00002",
+				"completed_qty": job_card.for_quantity
+			})
+			doc.submit()
 
-			if job_card:
-				workstation = frappe.db.get_value("Workstation",
-					{"name": ("not in", [job_card.workstation])}, "name")
+			completed_qty = frappe.db.get_value("Work Order Operation", job_card.operation_id, "completed_qty")
+			self.assertEqual(completed_qty, job_card.for_quantity)
 
-				if not workstation or job_card.workstation == workstation:
-					workstation = make_workstation(workstation_name=random_string(5)).name
-
-				doc = frappe.get_doc("Job Card", job_card.name)
-				doc.workstation = workstation
-				doc.append("time_logs", {
-					"from_time": "2009-01-01 12:06:25",
-					"to_time": "2009-01-01 12:37:25",
-					"time_in_mins": "31.00002",
-					"completed_qty": job_card.for_quantity
-				})
-				doc.submit()
-
-				completed_qty = frappe.db.get_value("Work Order Operation", job_card.operation_id, "completed_qty")
-				self.assertEqual(completed_qty, job_card.for_quantity)
-
-				doc.cancel()
+			doc.cancel()
 
 			for d in job_cards:
 				frappe.delete_doc("Job Card", d.name)
+
+	def test_job_card_overlap(self):
+		wo2 = make_wo_order_test_record(item="_Test FG Item 2", qty=2)
+
+		jc1_name = frappe.db.get_value("Job Card", {'work_order': self.work_order.name})
+		jc2_name = frappe.db.get_value("Job Card", {'work_order': wo2.name})
+
+		jc1 = frappe.get_doc("Job Card", jc1_name)
+		jc2 = frappe.get_doc("Job Card", jc2_name)
+
+		employee = "_T-Employee-00001" # from test records
+
+		jc1.append("time_logs", {
+			"from_time": "2021-01-01 00:00:00",
+			"to_time": "2021-01-01 08:00:00",
+			"completed_qty": 1,
+			"employee": employee,
+		})
+		jc1.save()
+
+		# add a new entry in same time slice
+		jc2.append("time_logs", {
+			"from_time": "2021-01-01 00:01:00",
+			"to_time": "2021-01-01 06:00:00",
+			"completed_qty": 1,
+			"employee": employee,
+		})
+		self.assertRaises(OverlapError, jc2.save)