diff --git a/src/pretix/api/serializers/event.py b/src/pretix/api/serializers/event.py
index 0cf4d4dcb2..b2ad11732b 100644
--- a/src/pretix/api/serializers/event.py
+++ b/src/pretix/api/serializers/event.py
@@ -971,21 +971,21 @@ class ItemMetaPropertiesSerializer(I18nAwareModelSerializer):
         fields = ('id', 'name', 'default', 'required', 'allowed_values')
 
 
-def prefetch_by_id(items, qs, id_attr, id_filter, target_attr):
+def prefetch_by_id(items, qs, id_attr, target_attr):
     """
     Prefetches a related object on each item in the given list of items by searching by id or another
-    unique field. The id value is read from the attribute on item specified in `id_attr`, searched on queryset `qs` by the
-    field specified in `id_filter`, and the resulting prefetched model object is stored into `target_attr` on the item.
+    unique field. The id value is read from the attribute on item specified in `id_attr`, searched on queryset `qs` by
+    the primary key, and the resulting prefetched model object is stored into `target_attr` on the item.
     """
     ids = [getattr(item, id_attr) for item in items if getattr(item, id_attr)]
     if ids:
-        result = qs.order_by(id_filter).distinct(id_filter).in_bulk(id_list=ids, field_name=id_filter)
+        result = qs.in_bulk(id_list=ids)
         for item in items:
             setattr(item, target_attr, result.get(getattr(item, id_attr)))
 
 
 class SeatSerializer(I18nAwareModelSerializer):
-    orderposition = serializers.CharField(source='orderposition_id')
+    orderposition = serializers.IntegerField(source='orderposition_id')
     cartposition = serializers.IntegerField(source='cartposition_id')
     voucher = serializers.IntegerField(source='voucher_id')
 
@@ -1004,11 +1004,11 @@ class SeatSerializer(I18nAwareModelSerializer):
 
     def prefetch_expanded_data(self, items, expand_fields, event):
         if 'orderposition' in expand_fields:
-            prefetch_by_id(items, OrderPosition.objects.prefetch_related('order'), 'orderposition_id', 'id', 'orderposition')
+            prefetch_by_id(items, OrderPosition.objects.prefetch_related('order'), 'orderposition_id', 'orderposition')
         if 'cartposition' in expand_fields:
-            prefetch_by_id(items, CartPosition.objects, 'cartposition_id', 'id', 'cartposition')
+            prefetch_by_id(items, CartPosition.objects, 'cartposition_id', 'cartposition')
         if 'voucher' in expand_fields:
-            prefetch_by_id(items, Voucher.objects, 'voucher_id', 'id', 'voucher')
+            prefetch_by_id(items, Voucher.objects, 'voucher_id', 'voucher')
 
     def __init__(self, instance, *args, **kwargs):
         if not kwargs.get('data'):
diff --git a/src/tests/api/test_events.py b/src/tests/api/test_events.py
index 4c0dae74a8..5c1918e7ca 100644
--- a/src/tests/api/test_events.py
+++ b/src/tests/api/test_events.py
@@ -999,6 +999,10 @@ def seatingplan(event, organizer, item):
 
 @pytest.mark.django_db
 def test_event_update_seating(token_client, organizer, event, item, seatingplan):
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/'.format(organizer.slug, event.slug))
+    assert resp.status_code == 200
+    assert len(resp.data['results']) == 0
+
     resp = token_client.patch(
         '/api/v1/organizers/{}/events/{}/'.format(organizer.slug, event.slug),
         {
@@ -1019,6 +1023,11 @@ def test_event_update_seating(token_client, organizer, event, item, seatingplan)
     assert m.layout_category == 'Stalls'
     assert m.product == item
 
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/'.format(organizer.slug, event.slug))
+    assert resp.status_code == 200
+    assert len(resp.data['results']) == 3
+    assert all(seat['product'] == item.pk for seat in resp.data['results'])
+
 
 @pytest.mark.django_db
 def test_event_update_seating_invalid_product(token_client, organizer, event, item, seatingplan):
@@ -1514,3 +1523,47 @@ def test_patch_event_settings_file(token_client, organizer, event):
     )
     assert resp.status_code == 200
     assert resp.data['logo_image'] is None
+
+
+@pytest.mark.django_db
+def test_event_block_unblock_seat(token_client, organizer, event, seatingplan, item):
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/events/{}/'.format(organizer.slug, event.slug),
+        {
+            "seating_plan": seatingplan.pk,
+            "seat_category_mapping": {
+                "Stalls": item.pk
+            }
+        },
+        format='json'
+    )
+    assert resp.status_code == 200
+    event.refresh_from_db()
+
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/'.format(organizer.slug, event.slug))
+    assert resp.status_code == 200
+
+    seat_id = resp.data['results'][0]['id']
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/events/{}/seats/{}/'.format(organizer.slug, event.slug, seat_id),
+        {
+            "blocked": True,
+        },
+        format='json'
+    )
+    assert resp.status_code == 200
+    assert resp.data['blocked'] is True
+
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/{}/?expand=orderposition&expand=cartposition&expand=voucher'.format(organizer.slug, event.slug, seat_id))
+    assert resp.status_code == 200
+    assert resp.data['blocked'] is True
+
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/events/{}/seats/{}/'.format(organizer.slug, event.slug, seat_id),
+        {
+            "blocked": False,
+        },
+        format='json'
+    )
+    assert resp.status_code == 200
+    assert resp.data['blocked'] is False
diff --git a/src/tests/api/test_order_create.py b/src/tests/api/test_order_create.py
index b52fbad1cb..029b227ab2 100644
--- a/src/tests/api/test_order_create.py
+++ b/src/tests/api/test_order_create.py
@@ -2010,6 +2010,15 @@ def test_order_create_with_seat(token_client, organizer, event, item, quota, sea
         p = o.positions.first()
     assert p.seat == seat
 
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/{}/'.format(organizer.slug, event.slug, seat.pk))
+    assert resp.status_code == 200
+    assert resp.data['orderposition'] == p.pk
+
+    resp = token_client.get('/api/v1/organizers/{}/events/{}/seats/{}/?expand=orderposition'.format(organizer.slug, event.slug, seat.pk))
+    assert resp.status_code == 200
+    assert resp.data['orderposition']['id'] == p.pk
+
+
 
 @pytest.mark.django_db
 def test_order_create_with_blocked_seat_allowed(token_client, organizer, event, item, quota, seat, question):
diff --git a/src/tests/api/test_permissions.py b/src/tests/api/test_permissions.py
index a96054c206..d85e0c99f0 100644
--- a/src/tests/api/test_permissions.py
+++ b/src/tests/api/test_permissions.py
@@ -54,6 +54,7 @@ event_urls = [
     (None, 'taxrules/'),
     ('can_view_orders', 'waitinglistentries/'),
     ('can_view_orders', 'checkinlists/'),
+    (None, 'seats/'),
 ]
 
 event_permission_sub_urls = [
@@ -191,6 +192,8 @@ event_permission_sub_urls = [
     ('post', 'can_change_event_settings', 'item_meta_properties/', 400),
     ('patch', 'can_change_event_settings', 'item_meta_properties/0/', 404),
     ('delete', 'can_change_event_settings', 'item_meta_properties/0/', 404),
+    ('get', None, 'seats/1/', 404),
+    ('patch', 'can_change_event_settings', 'seats/1/', 404),
 ]
 
 org_permission_sub_urls = [