diff --git a/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py b/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
index b4d584f..6deee38 100644
--- a/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
+++ b/erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py
@@ -20,11 +20,13 @@
 test_ignore = ["Serial No"]
 
 class TestPurchaseInvoice(unittest.TestCase):
-	def setUp(self):
+	@classmethod
+	def setUpClass(self):
 		unlink_payment_on_cancel_of_invoice()
 		frappe.db.set_value("Buying Settings", None, "allow_multiple_items", 1)
 
-	def tearDown(self):
+	@classmethod
+	def tearDownClass(self):
 		unlink_payment_on_cancel_of_invoice(0)
 
 	def test_gl_entries_without_perpetual_inventory(self):
@@ -91,6 +93,7 @@
 		pi_doc = frappe.get_doc('Purchase Invoice', pi_doc.name)
 
 		self.assertRaises(frappe.LinkExistsError, pi_doc.cancel)
+		unlink_payment_on_cancel_of_invoice()
 
 	def test_purchase_invoice_for_blocked_supplier(self):
 		supplier = frappe.get_doc('Supplier', '_Test Supplier')
diff --git a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
index 52470fd..dff5594 100644
--- a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
@@ -29,10 +29,12 @@
 		w.submit()
 		return w
 
-	def setUp(self):
+	@classmethod
+	def setUpClass(self):
 		unlink_payment_on_cancel_of_invoice()
 
-	def tearDown(self):
+	@classmethod
+	def tearDownClass(self):
 		unlink_payment_on_cancel_of_invoice(0)
 
 	def test_timestamp_change(self):
@@ -135,6 +137,7 @@
 		unlink_payment_on_cancel_of_invoice(0)
 		si = frappe.get_doc('Sales Invoice', si.name)
 		self.assertRaises(frappe.LinkExistsError, si.cancel)
+		unlink_payment_on_cancel_of_invoice()
 
 	def test_sales_invoice_calculation_export_currency(self):
 		si = frappe.copy_doc(test_records[2])