diff --git a/apps/user/models.py b/apps/user/models.py
index ef95c463..43eac1cd 100644
--- a/apps/user/models.py
+++ b/apps/user/models.py
@@ -67,8 +67,8 @@ class User(AbstractUser):
             models.Sum('amount'),
             models.Sum('commission'),
         )
-        amount = aggregate.get('amount__sum', 0)
-        commission = aggregate.get('commission__sum', 0)
+        amount = aggregate.get('amount__sum') or 0
+        commission = aggregate.get('commission__sum') or 0
         return amount - commission