diff --git a/npl_portfolio/counterparty.py b/npl_portfolio/counterparty.py
index b3dba97..36bf30b 100755
--- a/npl_portfolio/counterparty.py
+++ b/npl_portfolio/counterparty.py
@@ -343,3 +343,4 @@ def __str__(self):
     class Meta:
         verbose_name = "Counterparty"
         verbose_name_plural = "Counterparties"
+        unique_together = [['portfolio_id', 'counterparty_identifier']]