diff --git a/billard/models.py b/billard/models.py
index 54ce203..1289a72 100644
--- a/billard/models.py
+++ b/billard/models.py
@@ -127,16 +127,17 @@ def process_location_data():
             desk = desk[0]
             ac = desk.accounting_set.order_by('time_from').reverse()
             if ld.on_off:
+                acc = None
                 if ac.count() > 0 and ac[0].time_to is None:
-                    ac[0].time_to = ld.tst
-                    ac[0].save()
                     mail_admins(subject='Accounting passt nicht',
                                 message='Vorheriges Accounting nicht abgeschlossen: Desk_id {}, Accounting_id {}'
                                 .format(desk.id, ac[0].id))
-                acc = Accounting(
-                    desk=desk,
-                    time_from=ld.tst,
-                )
+                    acc = ac[0]
+                if acc is None:
+                    acc = Accounting(
+                        desk=desk,
+                        time_from=ld.tst,
+                    )
                 acc.save()
                 ld.delete()
             else: