diff --git a/src/pretix/api/serializers/checkin.py b/src/pretix/api/serializers/checkin.py
index be8746dfe..12a3adcb5 100644
--- a/src/pretix/api/serializers/checkin.py
+++ b/src/pretix/api/serializers/checkin.py
@@ -60,7 +60,7 @@ class CheckinListSerializer(I18nAwareModelSerializer):
         full_data = self.to_internal_value(self.to_representation(self.instance)) if self.instance else {}
         full_data.update(data)
 
-        for item in full_data.get('limit_products'):
+        for item in full_data.get('limit_products', []):
             if event != item.event:
                 raise ValidationError(_('One or more items do not belong to this event.'))
 
diff --git a/src/pretix/base/models/items.py b/src/pretix/base/models/items.py
index 1dc63fe9d..5c8aeb773 100644
--- a/src/pretix/base/models/items.py
+++ b/src/pretix/base/models/items.py
@@ -1697,7 +1697,7 @@ class Quota(LoggedModel):
             if event != item.event:
                 raise ValidationError(_('One or more items do not belong to this event.'))
             if item.has_variations:
-                if not any(var.item == item for var in variations):
+                if not variations or not any(var.item == item for var in variations):
                     raise ValidationError(_('One or more items has variations but none of these are in the variations list.'))
 
     @staticmethod