diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index 410f4c11e7..df7fb6aab7 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -69,7 +69,7 @@ class Auth(object):
 
             if not creation_event:
                 raise SynapseError(
-                    400,
+                    403,
                     "Room %r does not exist" % (event.room_id,)
                 )
 
diff --git a/tests/test_state.py b/tests/test_state.py
index 5845358754..55f37c521f 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -204,8 +204,8 @@ class StateTestCase(unittest.TestCase):
             nodes={
                 "START": DictObj(
                     type=EventTypes.Create,
-                    state_key="creator",
-                    content={"membership": "@user_id:example.com"},
+                    state_key="",
+                    content={"creator": "@user_id:example.com"},
                     depth=1,
                 ),
                 "A": DictObj(
@@ -259,8 +259,8 @@ class StateTestCase(unittest.TestCase):
             nodes={
                 "START": DictObj(
                     type=EventTypes.Create,
-                    state_key="creator",
-                    content={"membership": "@user_id:example.com"},
+                    state_key="",
+                    content={"creator": "@user_id:example.com"},
                     depth=1,
                 ),
                 "A": DictObj(
@@ -432,13 +432,19 @@ class StateTestCase(unittest.TestCase):
     def test_resolve_message_conflict(self):
         event = create_event(type="test_message", name="event")
 
+        creation = create_event(
+            type=EventTypes.Create, state_key=""
+        )
+
         old_state_1 = [
+            creation,
             create_event(type="test1", state_key="1"),
             create_event(type="test1", state_key="2"),
             create_event(type="test2", state_key=""),
         ]
 
         old_state_2 = [
+            creation,
             create_event(type="test1", state_key="1"),
             create_event(type="test3", state_key="2"),
             create_event(type="test4", state_key=""),
@@ -446,7 +452,7 @@ class StateTestCase(unittest.TestCase):
 
         context = yield self._get_context(event, old_state_1, old_state_2)
 
-        self.assertEqual(len(context.current_state), 5)
+        self.assertEqual(len(context.current_state), 6)
 
         self.assertIsNone(context.state_group)
 
@@ -454,13 +460,19 @@ class StateTestCase(unittest.TestCase):
     def test_resolve_state_conflict(self):
         event = create_event(type="test4", state_key="", name="event")
 
+        creation = create_event(
+            type=EventTypes.Create, state_key=""
+        )
+
         old_state_1 = [
+            creation,
             create_event(type="test1", state_key="1"),
             create_event(type="test1", state_key="2"),
             create_event(type="test2", state_key=""),
         ]
 
         old_state_2 = [
+            creation,
             create_event(type="test1", state_key="1"),
             create_event(type="test3", state_key="2"),
             create_event(type="test4", state_key=""),
@@ -468,7 +480,7 @@ class StateTestCase(unittest.TestCase):
 
         context = yield self._get_context(event, old_state_1, old_state_2)
 
-        self.assertEqual(len(context.current_state), 5)
+        self.assertEqual(len(context.current_state), 6)
 
         self.assertIsNone(context.state_group)
 
@@ -484,36 +496,45 @@ class StateTestCase(unittest.TestCase):
             }
         )
 
+        creation = create_event(
+            type=EventTypes.Create, state_key="",
+            content={"creator": "@foo:bar"}
+        )
+
         old_state_1 = [
+            creation,
             member_event,
             create_event(type="test1", state_key="1", depth=1),
         ]
 
         old_state_2 = [
+            creation,
             member_event,
             create_event(type="test1", state_key="1", depth=2),
         ]
 
         context = yield self._get_context(event, old_state_1, old_state_2)
 
-        self.assertEqual(old_state_2[1], context.current_state[("test1", "1")])
+        self.assertEqual(old_state_2[2], context.current_state[("test1", "1")])
 
         # Reverse the depth to make sure we are actually using the depths
         # during state resolution.
 
         old_state_1 = [
+            creation,
             member_event,
             create_event(type="test1", state_key="1", depth=2),
         ]
 
         old_state_2 = [
+            creation,
             member_event,
             create_event(type="test1", state_key="1", depth=1),
         ]
 
         context = yield self._get_context(event, old_state_1, old_state_2)
 
-        self.assertEqual(old_state_1[1], context.current_state[("test1", "1")])
+        self.assertEqual(old_state_1[2], context.current_state[("test1", "1")])
 
     def _get_context(self, event, old_state_1, old_state_2):
         group_name_1 = "group_name_1"