diff --git a/changelog.d/4447.misc b/changelog.d/4447.misc
new file mode 100644
index 000000000000..43f8963614b7
--- /dev/null
+++ b/changelog.d/4447.misc
@@ -0,0 +1 @@
+Add infrastructure to support different event formats
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 888296933b88..38470ad176b5 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -18,7 +18,7 @@
 
 import six
 
-from synapse.api.constants import EventFormatVersions
+from synapse.api.constants import KNOWN_ROOM_VERSIONS, EventFormatVersions
 from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
 
@@ -240,3 +240,19 @@ def __repr__(self):
             self.get("type", None),
             self.get("state_key", None),
         )
+
+
+def room_version_to_event_format(room_version):
+    """Converts a room version string to the event format
+
+    Args:
+        room_version (str)
+
+    Returns:
+        int
+    """
+    if room_version not in KNOWN_ROOM_VERSIONS:
+        # We should have already checked version, so this should not happen
+        raise RuntimeError("Unrecognized room version %s" % (room_version,))
+
+    return EventFormatVersions.V1
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 777deabdf7b5..33ecabca291d 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -38,6 +38,7 @@
     SynapseError,
 )
 from synapse.crypto.event_signing import add_hashes_and_signatures
+from synapse.events import room_version_to_event_format
 from synapse.federation.federation_base import FederationBase, event_from_pdu_json
 from synapse.util import logcontext, unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
@@ -557,9 +558,10 @@ def make_membership_event(self, destinations, room_id, user_id, membership,
             params (dict[str, str|Iterable[str]]): Query parameters to include in the
                 request.
         Return:
-            Deferred[tuple[str, FrozenEvent]]: resolves to a tuple of `origin`
-            and event where origin is the remote homeserver which generated
-            the event.
+            Deferred[tuple[str, FrozenEvent, int]]: resolves to a tuple of
+            `(origin, event, event_format)` where origin is the remote
+            homeserver which generated the event, and event_format is one of
+            `synapse.api.constants.EventFormatVersions`.
 
             Fails with a ``SynapseError`` if the chosen remote server
             returns a 300/400 code.
@@ -579,6 +581,11 @@ def send_request(destination):
                 destination, room_id, user_id, membership, params,
             )
 
+            # Note: If not supplied, the room version may be either v1 or v2,
+            # however either way the event format version will be v1.
+            room_version = ret.get("room_version", RoomVersions.V1)
+            event_format = room_version_to_event_format(room_version)
+
             pdu_dict = ret.get("event", None)
             if not isinstance(pdu_dict, dict):
                 raise InvalidResponseError("Bad 'event' field in response")
@@ -607,7 +614,7 @@ def send_request(destination):
             ev = builder.build()
 
             defer.returnValue(
-                (destination, ev)
+                (destination, ev, event_format)
             )
 
         return self._try_destination_list(
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index cb729c69ea6d..dde166e29502 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -400,8 +400,14 @@ def on_make_leave_request(self, origin, room_id, user_id):
         origin_host, _ = parse_server_name(origin)
         yield self.check_server_matches_acl(origin_host, room_id)
         pdu = yield self.handler.on_make_leave_request(room_id, user_id)
+
+        room_version = yield self.store.get_room_version(room_id)
+
         time_now = self._clock.time_msec()
-        defer.returnValue({"event": pdu.get_pdu_json(time_now)})
+        defer.returnValue({
+            "event": pdu.get_pdu_json(time_now),
+            "room_version": room_version,
+        })
 
     @defer.inlineCallbacks
     def on_send_leave_request(self, origin, content):
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 453d393ce1de..c52dca1b813b 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1336,7 +1336,7 @@ def do_remotely_reject_invite(self, target_hosts, room_id, user_id):
     @defer.inlineCallbacks
     def _make_and_verify_event(self, target_hosts, room_id, user_id, membership,
                                content={}, params=None):
-        origin, pdu = yield self.federation_client.make_membership_event(
+        origin, pdu, _ = yield self.federation_client.make_membership_event(
             target_hosts,
             room_id,
             user_id,