diff --git a/raiden/network/transport/matrix/transport.py b/raiden/network/transport/matrix/transport.py
index 6520a299725..3751774743e 100644
--- a/raiden/network/transport/matrix/transport.py
+++ b/raiden/network/transport/matrix/transport.py
@@ -440,27 +440,7 @@ def start(  # type: ignore
         self._initialize_room_inventory()
         self._initialize_broadcast_rooms()
         self._initialize_whitelist(whitelist)
-
-        broadcast_filter_id = self._client.create_sync_filter(
-            not_rooms=self._broadcast_rooms.values()
-        )
-        self._client.set_sync_filter_id(broadcast_filter_id)
-
-        def on_success(greenlet: gevent.Greenlet) -> None:
-            if greenlet in self.greenlets:
-                self.greenlets.remove(greenlet)
-
-        self._client.start_listener_thread(
-            timeout_ms=self._config.sync_timeout, latency_ms=self._config.sync_latency
-        )
-        assert isinstance(self._client.sync_worker, gevent.Greenlet)
-        self._client.sync_worker.link_exception(self.on_error)
-        self._client.sync_worker.link_value(on_success)
-
-        assert isinstance(self._client.message_worker, gevent.Greenlet)
-        self._client.message_worker.link_exception(self.on_error)
-        self._client.message_worker.link_value(on_success)
-        self.greenlets = [self._client.sync_worker, self._client.message_worker]
+        self._initialize_sync()
 
         # (re)start any _RetryQueue which was initialized before start
         for retrier in self._address_to_retrier.values():
@@ -851,15 +831,58 @@ def _initialize_broadcast_rooms(self) -> None:
         msg = "To join the broadcast rooms the Matrix client to be properly authenticated."
         assert self._user_id, msg
 
+        pool = Pool(size=10)
+
+        def _join_broadcast_room(client: GMatrixClient, broadcast_room_alias: str) -> None:
+            self.log.debug("Joining broadcast room", broadcast_room_alias=broadcast_room_alias)
+            self._broadcast_rooms[room_name] = join_broadcast_room(
+                client=client, broadcast_room_alias=broadcast_room_alias
+            )
+
         for suffix in self._config.broadcast_rooms:
             room_name = make_room_alias(self.chain_id, suffix)
             broadcast_room_alias = f"#{room_name}:{self._server_name}"
 
             if room_name not in self._broadcast_rooms:
-                self.log.debug("Joining broadcast room", broadcast_room_alias=broadcast_room_alias)
-                self._broadcast_rooms[room_name] = join_broadcast_room(
-                    client=self._client, broadcast_room_alias=broadcast_room_alias
-                )
+                pool.apply_async(_join_broadcast_room, args=(self._client, broadcast_room_alias))
+
+        pool.join(raise_error=True)
+
+    def _initialize_sync(self) -> None:
+        msg = "_initialize_sync requires the GMatrixClient to be properly authenticated."
+        assert self._user_id, msg
+
+        msg = "The sync thread must not be started twice"
+        assert self._client.sync_worker is None, msg
+        assert self._client.message_worker is None, msg
+
+        msg = (
+            "The node must have joined the broadcast rooms before starting the "
+            "sync thread, since that is necessary to properly generate the "
+            "filters."
+        )
+        assert self._broadcast_rooms, msg
+
+        broadcast_filter_id = self._client.create_sync_filter(
+            not_rooms=self._broadcast_rooms.values()
+        )
+        self._client.set_sync_filter_id(broadcast_filter_id)
+
+        def on_success(greenlet: gevent.Greenlet) -> None:
+            if greenlet in self.greenlets:
+                self.greenlets.remove(greenlet)
+
+        self._client.start_listener_thread(
+            timeout_ms=self._config.sync_timeout, latency_ms=self._config.sync_latency
+        )
+        assert isinstance(self._client.sync_worker, gevent.Greenlet)
+        self._client.sync_worker.link_exception(self.on_error)
+        self._client.sync_worker.link_value(on_success)
+
+        assert isinstance(self._client.message_worker, gevent.Greenlet)
+        self._client.message_worker.link_exception(self.on_error)
+        self._client.message_worker.link_value(on_success)
+        self.greenlets = [self._client.sync_worker, self._client.message_worker]
 
     def _initialize_whitelist(self, whitelist: List[Address]) -> None:
         msg = (