diff --git a/addons/payment_adyen/models/payment_transaction.py b/addons/payment_adyen/models/payment_transaction.py
index a3f7e78e55e..91a4da15737 100644
--- a/addons/payment_adyen/models/payment_transaction.py
+++ b/addons/payment_adyen/models/payment_transaction.py
@@ -173,7 +173,13 @@ class PaymentTransaction(models.Model):
             source_tx = self.search(
                 [('acquirer_reference', '=', source_acquirer_reference), ('provider', '=', 'adyen')]
             )
-            tx = self._adyen_create_refund_tx_from_feedback_data(source_tx, data)
+            if source_tx:
+                # Manually create a refund transaction with a new reference. The reference of
+                # the refund transaction was personalized from Adyen and could be identical to
+                # that of an existing transaction.
+                tx = self._adyen_create_refund_tx_from_feedback_data(source_tx, data)
+            else:  # The refund was initiated for an unknown source transaction
+                pass  # Don't do anything with the refund notification
 
         if not tx:
             raise ValidationError(