diff --git a/src/pretix/api/serializers/event.py b/src/pretix/api/serializers/event.py
index ea4116116..eaf674099 100644
--- a/src/pretix/api/serializers/event.py
+++ b/src/pretix/api/serializers/event.py
@@ -138,8 +138,11 @@ class EventSerializer(I18nAwareModelSerializer):
         return value
 
     def validate_seat_category_mapping(self, value):
-        if value and value['seat_category_mapping'] and (not self.instance or not self.instance.pk):
-            raise ValidationError('You cannot specify seat category mappings on event creation.')
+        if not self.instance or not self.instance.pk:
+            if value and value['seat_category_mapping']:
+                raise ValidationError('You cannot specify seat category mappings on event creation.')
+            else:
+                return {'seat_category_mapping': {}}
         item_cache = {i.pk: i for i in self.instance.items.all()}
         result = {}
         for k, item in value['seat_category_mapping'].items():
diff --git a/src/tests/api/test_events.py b/src/tests/api/test_events.py
index 21ff8b88f..798c52a5e 100644
--- a/src/tests/api/test_events.py
+++ b/src/tests/api/test_events.py
@@ -176,6 +176,7 @@ def test_event_create(token_client, organizer, event, meta_prop):
             "meta_data": {
                 meta_prop.name: "Conference"
             },
+            "seat_category_mapping": {},
             "timezone": "Europe/Amsterdam"
         },
         format='json'