diff --git a/erpnext/accounts/doctype/cashier_closing/test_cashier_closing.py b/erpnext/accounts/doctype/cashier_closing/test_cashier_closing.py
index 34aa85d65fc..e7a9ffc3d10 100644
--- a/erpnext/accounts/doctype/cashier_closing/test_cashier_closing.py
+++ b/erpnext/accounts/doctype/cashier_closing/test_cashier_closing.py
@@ -20,6 +20,7 @@ class TestCashierClosing(ERPNextTestSuite):
 		si = create_sales_invoice(rate=rate, qty=1, posting_date=DATE, do_not_submit=True)
 		si.posting_time = "10:30:00"
 		si.submit()
+		si.reload()  # read outstanding_amount as persisted after submit
 		return si
 
 	def make_closing(self, user="Administrator", payments=None, **args):
@@ -39,6 +40,11 @@ class TestCashierClosing(ERPNextTestSuite):
 		doc = self.make_closing(from_time="18:00:00", time="09:00:00")
 		self.assertRaises(frappe.ValidationError, doc.save)
 
+	def test_equal_from_and_to_time_is_rejected(self):
+		# validate_time uses >=, so a zero-length window is also blocked
+		doc = self.make_closing(from_time="09:00:00", time="09:00:00")
+		self.assertRaises(frappe.ValidationError, doc.save)
+
 	def test_net_amount_rolls_up_outstanding_and_adjustments(self):
 		si = self.make_invoice_in_window(rate=100)
 		doc = self.make_closing(payments=[500], expense=50, custody=30, returns=20)