diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index d05ed91d64..8fa726759e 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -32,7 +32,6 @@ from synapse.api.errors import (
     HttpResponseException,
     SynapseError,
 )
-from synapse.events import builder
 from synapse.federation.federation_base import FederationBase, event_from_pdu_json
 from synapse.util import logcontext, unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
@@ -66,6 +65,8 @@ class FederationClient(FederationBase):
         self.state = hs.get_state_handler()
         self.transport_layer = hs.get_federation_transport_client()
 
+        self.event_builder_factory = hs.get_event_builder_factory()
+
         self._get_pdu_cache = ExpiringCache(
             cache_name="get_pdu_cache",
             clock=self._clock,
@@ -571,7 +572,12 @@ class FederationClient(FederationBase):
             if "prev_state" not in pdu_dict:
                 pdu_dict["prev_state"] = []
 
-            ev = builder.EventBuilder(pdu_dict)
+            # Strip off the fields that we want to clobber.
+            pdu_dict.pop("origin", None)
+            pdu_dict.pop("origin_server_ts", None)
+            pdu_dict.pop("unsigned", None)
+
+            ev = self.event_builder_factory.new(pdu_dict)
 
             defer.returnValue(
                 (destination, ev)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index a3bb864bb2..70be87cd3d 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -43,10 +43,7 @@ from synapse.api.errors import (
     StoreError,
     SynapseError,
 )
-from synapse.crypto.event_signing import (
-    add_hashes_and_signatures,
-    compute_event_signature,
-)
+from synapse.crypto.event_signing import compute_event_signature
 from synapse.events.validator import EventValidator
 from synapse.replication.http.federation import (
     ReplicationCleanRoomRestServlet,
@@ -58,7 +55,6 @@ from synapse.types import UserID, get_domain_from_id
 from synapse.util import logcontext, unwrapFirstError
 from synapse.util.async_helpers import Linearizer
 from synapse.util.distributor import user_joined_room
-from synapse.util.frozenutils import unfreeze
 from synapse.util.logutils import log_function
 from synapse.util.retryutils import NotRetryingDestination
 from synapse.visibility import filter_events_for_server
@@ -1083,7 +1079,9 @@ class FederationHandler(BaseHandler):
         handled_events = set()
 
         try:
-            event = self._sign_event(event)
+            self._sign_event(event)
+            event.internal_metadata.outlier = False
+
             # Try the host we successfully got a response to /make_join/
             # request first.
             try:
@@ -1289,13 +1287,7 @@ class FederationHandler(BaseHandler):
         event.internal_metadata.outlier = True
         event.internal_metadata.invite_from_remote = True
 
-        event.signatures.update(
-            compute_event_signature(
-                event,
-                self.hs.hostname,
-                self.hs.config.signing_key[0]
-            )
-        )
+        self._sign_event(event)
 
         context = yield self.state_handler.compute_event_context(event)
         yield self.persist_events_and_notify([(event, context)])
@@ -1313,7 +1305,7 @@ class FederationHandler(BaseHandler):
         # Mark as outlier as we don't have any state for this event; we're not
         # even in the room.
         event.internal_metadata.outlier = True
-        event = self._sign_event(event)
+        self._sign_event(event)
 
         # Try the host that we succesfully called /make_leave/ on first for
         # the /send_leave/ request.
@@ -1358,26 +1350,14 @@ class FederationHandler(BaseHandler):
         defer.returnValue((origin, event))
 
     def _sign_event(self, event):
-        event.internal_metadata.outlier = False
-
-        builder = self.event_builder_factory.new(
-            unfreeze(event.get_pdu_json())
+        event.signatures.update(
+            compute_event_signature(
+                event,
+                self.hs.hostname,
+                self.hs.config.signing_key[0]
+            )
         )
 
-        builder.event_id = self.event_builder_factory.create_event_id()
-        builder.origin = self.hs.hostname
-
-        if not hasattr(event, "signatures"):
-            builder.signatures = {}
-
-        add_hashes_and_signatures(
-            builder,
-            self.hs.hostname,
-            self.hs.config.signing_key[0],
-        )
-
-        return builder.build()
-
     @defer.inlineCallbacks
     @log_function
     def on_make_leave_request(self, room_id, user_id):
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 0707f9a86a..c7488f4259 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -591,10 +591,7 @@ class RoomMemberStore(RoomMemberWorkerStore):
             # i.e., its something that has just happened.
             # The only current event that can also be an outlier is if its an
             # invite that has come in across federation.
-            is_new_state = not backfilled and (
-                not event.internal_metadata.is_outlier()
-                or event.internal_metadata.is_invite_from_remote()
-            )
+            is_new_state = not backfilled
             is_mine = self.hs.is_mine_id(event.state_key)
             if is_new_state and is_mine:
                 if event.membership == Membership.INVITE: