diff --git a/src/pretix/presale/views/__init__.py b/src/pretix/presale/views/__init__.py
index dc01c52997..b8d6acb691 100644
--- a/src/pretix/presale/views/__init__.py
+++ b/src/pretix/presale/views/__init__.py
@@ -229,7 +229,7 @@ class CartMixin:
 
         try:
             first_expiry = min(p.expires for p in positions) if positions else now()
-            max_expiry_extend = min(p.max_extend for p in positions) if positions else now()
+            max_expiry_extend = min((p.max_extend for p in positions if p.max_extend), default=None)
             total_seconds_left = max(first_expiry - now(), timedelta()).total_seconds()
             minutes_left = int(total_seconds_left // 60)
             seconds_left = int(total_seconds_left % 60)