diff --git a/src/c3nav/editor/migrations/0021_auto_20180918_1736.py b/src/c3nav/editor/migrations/0021_auto_20180918_1736.py
new file mode 100644
index 00000000..f85ab19d
--- /dev/null
+++ b/src/c3nav/editor/migrations/0021_auto_20180918_1736.py
@@ -0,0 +1,24 @@
+# Generated by Django 2.1.1 on 2018-09-18 15:36
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('editor', '0020_remove_permissions'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='changeset',
+            name='last_cleaned_with',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='checked_changesets', to='mapdata.MapUpdate'),
+        ),
+        migrations.AlterField(
+            model_name='changeset',
+            name='map_update',
+            field=models.OneToOneField(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='changeset', to='mapdata.MapUpdate', verbose_name='map update'),
+        ),
+    ]
diff --git a/src/c3nav/editor/models/changeset.py b/src/c3nav/editor/models/changeset.py
index bfe5425f..6746e8ee 100644
--- a/src/c3nav/editor/models/changeset.py
+++ b/src/c3nav/editor/models/changeset.py
@@ -38,11 +38,11 @@ class ChangeSet(models.Model):
     )
     created = models.DateTimeField(auto_now_add=True, verbose_name=_('created'))
     last_change = models.ForeignKey('editor.ChangeSetUpdate', null=True, related_name='+',
-                                    verbose_name=_('last object change'), on_delete=models.PROTECT)
+                                    verbose_name=_('last object change'), on_delete=models.CASCADE)
     last_update = models.ForeignKey('editor.ChangeSetUpdate', null=True, related_name='+',
-                                    verbose_name=_('last update'), on_delete=models.PROTECT)
+                                    verbose_name=_('last update'), on_delete=models.CASCADE)
     last_state_update = models.ForeignKey('editor.ChangeSetUpdate', null=True, related_name='+',
-                                          verbose_name=_('last state update'), on_delete=models.PROTECT)
+                                          verbose_name=_('last state update'), on_delete=models.CASCADE)
     state = models.CharField(max_length=20, db_index=True, choices=STATES, default='unproposed')
     author = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, on_delete=models.PROTECT, verbose_name=_('Author'))
     title = models.CharField(max_length=100, default='', verbose_name=_('Title'))
diff --git a/src/c3nav/editor/wrappers.py b/src/c3nav/editor/wrappers.py
index 67ea7cc6..57d94d61 100644
--- a/src/c3nav/editor/wrappers.py
+++ b/src/c3nav/editor/wrappers.py
@@ -206,8 +206,8 @@ class ModelInstanceWrapper(BaseWrapper):
         descriptor = getattr(self._obj.__class__, name, None)
         if isinstance(descriptor, ReverseOneToOneDescriptor):
             try:
-                rel_obj = getattr(self._obj, descriptor.cache_name)
-            except AttributeError:
+                rel_obj = descriptor.related.get_cached_value(self._obj)
+            except KeyError:
                 related_pk = self._obj._get_pk_val()
                 if related_pk is None:
                     rel_obj = None
@@ -219,8 +219,8 @@ class ModelInstanceWrapper(BaseWrapper):
                     except related_model.DoesNotExist:
                         rel_obj = None
                     else:
-                        setattr(rel_obj, descriptor.related.field.get_cache_name(), self._obj)
-                setattr(self._obj, descriptor.cache_name, rel_obj)
+                        descriptor.related.field.set_cached_value(rel_obj, self._obj)
+                descriptor.related.set_cached_value(self._obj, rel_obj)
         return super().__getattr__(name)
 
     def __setattr__(self, name, value):
@@ -241,7 +241,7 @@ class ModelInstanceWrapper(BaseWrapper):
                 if not isinstance(value, ModelInstanceWrapper):
                     raise ValueError('value has to be None or ModelInstanceWrapper')
                 setattr(self._obj, name, value._obj)
-                setattr(self._obj, field.get_cache_name(), value)
+                field.set_cached_value(self._obj, value)
                 return
         super().__setattr__(name, value)
 
@@ -368,6 +368,15 @@ class BaseQueryWrapper(BaseWrapper):
 
         return lookup_querysets[()]
 
+    def _chain(self, **kwargs):
+        """
+        Return a copy of the current QuerySet that's ready for another
+        operation.
+        """
+        obj = self._clone()
+        obj._obj.__dict__.update(kwargs)
+        return obj
+
     def _clone(self, **kwargs):
         clone = self._wrap_queryset(self._obj)
         clone._obj.__dict__.update(kwargs)
diff --git a/src/c3nav/mapdata/migrations/0070_auto_20180918_1736.py b/src/c3nav/mapdata/migrations/0070_auto_20180918_1736.py
new file mode 100644
index 00000000..9cc01a51
--- /dev/null
+++ b/src/c3nav/mapdata/migrations/0070_auto_20180918_1736.py
@@ -0,0 +1,54 @@
+# Generated by Django 2.1.1 on 2018-09-18 15:36
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mapdata', '0069_mapupdate_geometries_changed'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='area',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='areas', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='door',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='doors', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='graphedge',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='graphedges', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='level',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='levels', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='locationgroup',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='locationgroups', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='poi',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='pois', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='source',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='sources', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+        migrations.AlterField(
+            model_name='space',
+            name='access_restriction',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='spaces', to='mapdata.AccessRestriction', verbose_name='Access Restriction'),
+        ),
+    ]