diff --git a/src/pretix/control/views/orders.py b/src/pretix/control/views/orders.py
index 5edbceab3..e916c70b9 100644
--- a/src/pretix/control/views/orders.py
+++ b/src/pretix/control/views/orders.py
@@ -163,7 +163,7 @@ class OrderDetail(OrderView):
             'item', 'variation'
         ).prefetch_related(
             'item__questions', 'answers', 'answers__question'
-        )
+        ).order_by('positionid')
 
         positions = []
         for p in cartpos:
diff --git a/src/pretix/presale/views/__init__.py b/src/pretix/presale/views/__init__.py
index 1d077c5aa..171240330 100644
--- a/src/pretix/presale/views/__init__.py
+++ b/src/pretix/presale/views/__init__.py
@@ -40,10 +40,10 @@ class CartMixin:
         # Django is unable to join related models in a .values() query
         def keyfunc(pos):
             if downloads:
-                return pos.id, 0, 0, 0, 0
+                return pos.positionid, 0, 0, 0, 0
             if answers and ((pos.item.admission and self.request.event.settings.attendee_names_asked)
                             or pos.item.questions.all()):
-                return pos.id, 0, 0, 0, 0
+                return pos.positionid, 0, 0, 0, 0
             return 0, pos.item_id, pos.variation_id, pos.price, (pos.voucher_id or 0)
 
         positions = []