diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index f3924e23d8..5012c10ee8 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -454,7 +454,7 @@ class Keyring(object):
                 )
 
             processed_response = yield self.process_v2_response(
-                perspective_name, response
+                perspective_name, response, only_from_server=False
             )
 
             for server_name, response_keys in processed_response.items():
@@ -534,7 +534,7 @@ class Keyring(object):
 
     @defer.inlineCallbacks
     def process_v2_response(self, from_server, response_json,
-                            requested_ids=[]):
+                            requested_ids=[], only_from_server=True):
         time_now_ms = self.clock.time_msec()
         response_keys = {}
         verify_keys = {}
@@ -558,6 +558,13 @@ class Keyring(object):
 
         results = {}
         server_name = response_json["server_name"]
+        if only_from_server:
+            if server_name != from_server:
+                raise ValueError(
+                    "Expected a response for server %r not %r" % (
+                        from_server, server_name
+                    )
+                )
         for key_id in response_json["signatures"].get(server_name, {}):
             if key_id not in response_json["verify_keys"]:
                 raise ValueError(
diff --git a/synapse/storage/transactions.py b/synapse/storage/transactions.py
index 6c7481a728..6258ff1725 100644
--- a/synapse/storage/transactions.py
+++ b/synapse/storage/transactions.py
@@ -24,6 +24,7 @@ from collections import namedtuple
 
 import itertools
 import logging
+import ujson as json
 
 logger = logging.getLogger(__name__)
 
@@ -101,7 +102,7 @@ class TransactionStore(SQLBaseStore):
         )
 
         if result and result["response_code"]:
-            return result["response_code"], result["response_json"]
+            return result["response_code"], json.loads(str(result["response_json"]))
         else:
             return None