diff --git a/paypal/standard/helpers.py b/paypal/standard/helpers.py
index 4cf0f34..60d8f8f 100644
--- a/paypal/standard/helpers.py
+++ b/paypal/standard/helpers.py
@@ -24,6 +24,7 @@ def duplicate_txn_id(ipn_obj):
     similars = (ipn_obj._default_manager
                 .filter(txn_id=ipn_obj.txn_id)
                 .exclude(id=ipn_obj.id)
+                .exclude(flag=True)
                 .order_by('-created_at')[:1])
 
     if len(similars) > 0:
diff --git a/paypal/standard/ipn/tests/test_ipn.py b/paypal/standard/ipn/tests/test_ipn.py
index 859bdae..8eb8d97 100644
--- a/paypal/standard/ipn/tests/test_ipn.py
+++ b/paypal/standard/ipn/tests/test_ipn.py
@@ -259,6 +259,16 @@ def test_duplicate_txn_id(self):
         self.assertEqual(ipn_obj.flag, True)
         self.assertEqual(ipn_obj.flag_info, "Duplicate txn_id. (51403485VH153354B)")
 
+    def test_duplicate_txn_id_with_first_flagged(self):
+        PayPalIPN._postback = lambda self: b"Internal Server Error"
+        self.paypal_post(IPN_POST_PARAMS)
+        PayPalIPN._postback = lambda self: b"VERIFIED"
+        self.paypal_post(IPN_POST_PARAMS)
+        self.assertEqual(len(PayPalIPN.objects.all()), 2)
+        ipn_objs = PayPalIPN.objects.order_by('created_at', 'pk')
+        self.assertEqual(ipn_objs[0].flag, True)
+        self.assertEqual(ipn_objs[1].flag, False)
+
     def test_recurring_payment_skipped_ipn(self):
         update = {
             "recurring_payment_id": "BN5JZ2V7MLEV4",