diff --git a/src/pretix/base/pdf.py b/src/pretix/base/pdf.py
index 475afa3033..07459186eb 100644
--- a/src/pretix/base/pdf.py
+++ b/src/pretix/base/pdf.py
@@ -162,7 +162,7 @@ DEFAULT_VARIABLES = OrderedDict((
         "evaluate": lambda op, order, ev: "<br/>".join([
             '{} - {}'.format(p.item, p.variation) if p.variation else str(p.item)
             for p in (
-                op.addons.all() if 'addons' in op._prefetched_objects_cache
+                op.addons.all() if 'addons' in getattr(op, '_prefetched_objects_cache', {})
                 else op.addons.select_related('item', 'variation')
             )
         ])
diff --git a/src/pretix/plugins/ticketoutputpdf/signals.py b/src/pretix/plugins/ticketoutputpdf/signals.py
index a5a1c02368..8f2944569b 100644
--- a/src/pretix/plugins/ticketoutputpdf/signals.py
+++ b/src/pretix/plugins/ticketoutputpdf/signals.py
@@ -36,7 +36,7 @@ def register_data(sender, **kwargs):
 
 def get_answer(op, order, event, question_id):
     try:
-        if 'answers' in op._prefetched_objects_cache:
+        if 'answers' in getattr(op, '_prefetched_objects_cache', {}):
             a = [a for a in op.answers.all() if a.question_id == question_id][0]
         else:
             a = op.answers.get(question_id=question_id)