diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 24c2b2fad..7088c20cb 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -17,6 +17,7 @@ from ._base import BaseHandler
 
 from synapse.streams.config import PaginationConfig
 from synapse.api.constants import Membership, EventTypes
+from synapse.util import unwrapFirstError
 
 from twisted.internet import defer
 
@@ -209,9 +210,10 @@ class SyncHandler(BaseHandler):
         joined = []
         invited = []
         archived = []
+        deferreds = []
         for event in room_list:
             if event.membership == Membership.JOIN:
-                room_sync = yield self.full_state_sync_for_joined_room(
+                room_sync_deferred = self.full_state_sync_for_joined_room(
                     room_id=event.room_id,
                     sync_config=sync_config,
                     now_token=now_token,
@@ -220,7 +222,8 @@ class SyncHandler(BaseHandler):
                     tags_by_room=tags_by_room,
                     account_data_by_room=account_data_by_room,
                 )
-                joined.append(room_sync)
+                room_sync_deferred.addCallback(joined.append)
+                deferreds.append(room_sync_deferred)
             elif event.membership == Membership.INVITE:
                 invite = yield self.store.get_event(event.event_id)
                 invited.append(InvitedSyncResult(
@@ -231,7 +234,7 @@ class SyncHandler(BaseHandler):
                 leave_token = now_token.copy_and_replace(
                     "room_key", "s%d" % (event.stream_ordering,)
                 )
-                room_sync = yield self.full_state_sync_for_archived_room(
+                room_sync_deferred = self.full_state_sync_for_archived_room(
                     sync_config=sync_config,
                     room_id=event.room_id,
                     leave_event_id=event.event_id,
@@ -240,7 +243,12 @@ class SyncHandler(BaseHandler):
                     tags_by_room=tags_by_room,
                     account_data_by_room=account_data_by_room,
                 )
-                archived.append(room_sync)
+                room_sync_deferred.addCallback(archived.append)
+                deferreds.append(room_sync_deferred)
+
+        yield defer.gatherResults(
+            deferreds, consumeErrors=True
+        ).addErrback(unwrapFirstError)
 
         defer.returnValue(SyncResult(
             presence=presence,