diff --git a/src/pretix/base/models/invoices.py b/src/pretix/base/models/invoices.py
index e2f02d96c..d54d773e4 100644
--- a/src/pretix/base/models/invoices.py
+++ b/src/pretix/base/models/invoices.py
@@ -9,7 +9,7 @@ from django.db.models import Max
 
 def invoice_filename(instance, filename: str) -> str:
     secret = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(14))
-    return 'invoices/{org}/{ev}/{ev}-{no}-{code}-{secret}.pdf'.format(
+    return 'invoices/{org}/{ev}/{ev}-{no:05d}-{code}-{secret}.pdf'.format(
         org=instance.event.organizer.slug, ev=instance.event.slug,
         no=instance.invoice_no, code=instance.order.code,
         secret=secret
diff --git a/src/pretix/base/settings.py b/src/pretix/base/settings.py
index d205bcda8..938d53b1a 100644
--- a/src/pretix/base/settings.py
+++ b/src/pretix/base/settings.py
@@ -67,7 +67,7 @@ DEFAULTS = {
     },
     'invoice_generate': {
         'default': 'False',
-        'type': bool
+        'type': str
     },
     'invoice_address_from': {
         'default': '',
diff --git a/src/pretix/presale/templates/pretixpresale/event/checkout_questions.html b/src/pretix/presale/templates/pretixpresale/event/checkout_questions.html
index bce73e22e..fff072084 100644
--- a/src/pretix/presale/templates/pretixpresale/event/checkout_questions.html
+++ b/src/pretix/presale/templates/pretixpresale/event/checkout_questions.html
@@ -28,6 +28,9 @@
                         <h4 class="panel-title">
                             <a data-toggle="collapse" href="#invoice" data-parent="#questions_accordion">
                                 <strong>{% trans "Invoice information" %}</strong>
+                                {% if not event.settings.invoice_address_required %}
+                                    {% trans "(optional)" %}
+                                {% endif %}
                             </a>
                         </h4>
                     </div>