diff --git a/src/pretix/base/settings.py b/src/pretix/base/settings.py
index d225a2590c..60606f3011 100644
--- a/src/pretix/base/settings.py
+++ b/src/pretix/base/settings.py
@@ -555,9 +555,11 @@ DEFAULTS = {
         'serializer_class': serializers.IntegerField,
         'serializer_kwargs': dict(
             min_value=0,
+            max_value=60 * 24 * 7,
         ),
         'form_kwargs': dict(
             min_value=0,
+            max_value=60 * 24 * 7,
             label=_("Reservation period"),
             required=True,
             help_text=_("The number of minutes the items in a user's cart are reserved for this user."),