diff --git a/src/oscar_accounts/abstract_models.py b/src/oscar_accounts/abstract_models.py
index 35c9535..ed4373a 100644
--- a/src/oscar_accounts/abstract_models.py
+++ b/src/oscar_accounts/abstract_models.py
@@ -146,8 +146,10 @@ def save(self, *args, **kwargs):
         if self.code:
             self.code = self.code.upper()
         # Ensure the balance is always correct when saving
-        self.balance = self._balance()
-        return super().save(*args, **kwargs)
+        # Django 4.2 requires a pk to use manager methods as in self._balance()
+        if self.pk is not None:
+            self.balance = self._balance()
+        super().save(*args, **kwargs)
 
     def _balance(self):
         aggregates = self.transactions.aggregate(sum=Sum('amount'))