diff --git a/billard/models.py b/billard/models.py
index c431663..4ebf838 100644
--- a/billard/models.py
+++ b/billard/models.py
@@ -56,11 +56,12 @@ class Client(models.Model):
 
     def accounting_for(self, desk_no, pht, pnt):
         t = Accounting.objects.filter(client_id=self.id, desk_no=desk_no)[:3][::-1]
-        a = t[t.__len__() - 1]
-        if a.time_to is None:
-            prize = utils.get_prize_for(start=a.time_from, end=datetime.now(timezone.utc), pph=pht)
-            if prize != a.prize:
-                a.prize = prize
+        if t.__len__() > 0:
+            a = t[t.__len__() - 1]
+            if a.time_to is None:
+                prize = utils.get_prize_for(start=a.time_from, end=datetime.now(timezone.utc), pph=pht)
+                if prize != a.prize:
+                    a.prize = prize
         return t
 
     def accounting_1(self):