diff --git a/src/pretix/plugins/ticketoutputpdf/signals.py b/src/pretix/plugins/ticketoutputpdf/signals.py
index 1361d7531..9d05460da 100644
--- a/src/pretix/plugins/ticketoutputpdf/signals.py
+++ b/src/pretix/plugins/ticketoutputpdf/signals.py
@@ -102,9 +102,15 @@ def pdf_event_copy_data_receiver(sender, other, item_map, question_map, **kwargs
         for o in layout:
             if o['type'] == 'textarea':
                 if o['content'].startswith('question_'):
-                    newq = question_map.get(int(o['content'][9:]))
-                    if newq:
-                        o['content'] = 'question_{}'.format(newq.pk)
+                    try:
+                        newq = question_map.get(int(o['content'][9:]))
+                    except ValueError:
+                        # int cannot convert new placeholders question_{identifier}
+                        # can be safely ignored as only old format questions_{pk} should be converted
+                        pass
+                    else:
+                        if newq:
+                            o['content'] = 'question_{}'.format(newq.pk)
         bl.layout = json.dumps(layout)
 
         bl.save()