diff --git a/src/pretix/base/models/invoices.py b/src/pretix/base/models/invoices.py
index 695f512fb2..60e16a5b4f 100644
--- a/src/pretix/base/models/invoices.py
+++ b/src/pretix/base/models/invoices.py
@@ -122,6 +122,7 @@ class Invoice(models.Model):
 
     class Meta:
         unique_together = ('event', 'invoice_no')
+        ordering = ('invoice_no',)
 
 
 class InvoiceLine(models.Model):
diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index 17eb093b01..922e35c04c 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -479,6 +479,7 @@ class OrderPosition(AbstractPosition):
     class Meta:
         verbose_name = _("Order position")
         verbose_name_plural = _("Order positions")
+        ordering = ("positionid",)
 
     @classmethod
     def transform_cart_positions(cls, cp: List, order) -> list: