diff --git a/goodtimes/services.py b/goodtimes/services.py
index 1fa535f..42b7cf0 100644
--- a/goodtimes/services.py
+++ b/goodtimes/services.py
@@ -378,7 +378,7 @@ class PaymentProcessingService:
         )
 
         # Create a new subscription for the referred principal
-        referred_subscription_id = self.principal_subscription
+        referred_subscription_id = self.principal_subscription.id
 
         # Create or update the ReferralTracking record
         ReferralTracking.objects.create(