diff --git a/src/pretix/base/services/cart.py b/src/pretix/base/services/cart.py
index 6080378f08..59abf6c878 100644
--- a/src/pretix/base/services/cart.py
+++ b/src/pretix/base/services/cart.py
@@ -334,7 +334,8 @@ def _check_position_constraints(
         raise CartPositionError(error_messages['voucher_invalid_subevent'])
 
     # Voucher expired
-    if voucher and voucher.valid_until and voucher.valid_until < time_machine_now_dt:
+    # (checked using real_now_dt as vouchers influence quota calculations)
+    if voucher and voucher.valid_until and voucher.valid_until < real_now_dt:
         raise CartPositionError(error_messages['voucher_expired'])
 
     # Subevent has been disabled
diff --git a/src/pretix/presale/templates/pretixpresale/event/timemachine.html b/src/pretix/presale/templates/pretixpresale/event/timemachine.html
index d06f28b5fc..275d1f5d62 100644
--- a/src/pretix/presale/templates/pretixpresale/event/timemachine.html
+++ b/src/pretix/presale/templates/pretixpresale/event/timemachine.html
@@ -20,6 +20,7 @@
                 {% bootstrap_form_errors timemachine_form "all" %}
 
                 <p>{% trans "Test your shop as if it were a different date and time." %}</p>
+                <p>{% trans "Please note that the changed time is not taken into account for aspects of the shop that affect quotas, such as the validity period of carts and vouchers." %}</p>
 
                 <div class="row">
                     <div class="col-md-6">
@@ -44,4 +45,4 @@
             <div class="clear"></div>
         </div>
     </div>
-{% endblock %}
\ No newline at end of file
+{% endblock %}