diff --git a/api.py b/api.py
index 3c5cb7f..0f46eed 100644
--- a/api.py
+++ b/api.py
@@ -32,7 +32,7 @@ class InvalidInstanceID(Exception):
 
 
 def CreateChannel(google_user, client, instance_id, args):
-  models.Instance.FindOrCreate(instance_id, client)
+  models.Instance.FindOrCreate(instance_id)
 
   token = channel.create_channel(
       client_id=instance_id,
@@ -95,7 +95,7 @@ def Subscribe(google_user, client, instance_id, args):
     ret = {
       'result': 'ok',
       'events': models.Subscription.FindOrCreate(
-          subject, instance, messages, last_id),
+          subject, client, instance, messages, last_id),
     }
   except models.AccessDenied:
     logging.exception('Subscribe access denied')
diff --git a/channel.py b/channel.py
index 7d84690..39db032 100644
--- a/channel.py
+++ b/channel.py
@@ -33,17 +33,23 @@ class OnChannelConnect(webapp2.RequestHandler):
 
 
 class OnChannelDisconnect(webapp2.RequestHandler):
+  @staticmethod
+  @db.transactional()
+  def DeleteInstance(instance_id):
+    instance = models.Instance.FromID(instance_id)
+    ret = instance.key()
+    instance.delete()
+    return ret
+
   @utils.local_namespace
   def post(self):
     instance_id = self.request.get('from')
-    instance = models.Instance.FromID(instance_id)
+    instance_key = self.DeleteInstance(instance_id)
 
-    subscriptions = models.Subscription.all().filter('instance =', instance)
+    subscriptions = models.Subscription.all().filter('instance =', instance_key)
     for subscription in subscriptions:
       subscription.delete()
 
-    instance.delete()
-
 
 app = webapp2.WSGIApplication([
   ('/_ah/channel/connected/', OnChannelConnect),
diff --git a/lib/models.py b/lib/models.py
index 32b221f..1328e62 100644
--- a/lib/models.py
+++ b/lib/models.py
@@ -87,24 +87,21 @@ class Client(db.Model):
 
 
 class Instance(db.Model):
-  client = db.ReferenceProperty(required=True)
   active = db.BooleanProperty(required=True, default=False)
 
   @classmethod
   @db.transactional()
   def FromID(cls, instance_id):
-    # TODO: assert client equality here if possible
     return cls.get_by_key_name(instance_id)
 
   @classmethod
   @db.transactional()
-  def FindOrCreate(cls, instance_id, client):
+  def FindOrCreate(cls, instance_id):
     instance = cls.get_by_key_name(instance_id)
     if instance:
-      # TODO: assert client equality here
       return instance
     else:
-      return cls(key_name=instance_id, client=client).put()
+      return cls(key_name=instance_id).put()
 
 
 class Subject(db.Model):
@@ -242,13 +239,11 @@ class Subscription(db.Model):
 
   @classmethod
   @db.transactional()
-  def FindOrCreate(cls, subject, instance, messages=0, last_id=None):
+  def FindOrCreate(cls, subject, client, instance, messages=0, last_id=None):
     readable_only_by = (
         Subject.readable_only_by.get_value_for_datastore(subject))
-    client_key = (
-        Instance.client.get_value_for_datastore(instance))
     if (readable_only_by and
-        readable_only_by != client_key.parent()):
+        readable_only_by != client.parent_key()):
       raise AccessDenied
 
     subscriptions = (