diff --git a/docs/tcp_replication.rst b/docs/tcp_replication.rst
index 73436cea62..75e723484c 100644
--- a/docs/tcp_replication.rst
+++ b/docs/tcp_replication.rst
@@ -188,7 +188,9 @@ RDATA (S)
     A single update in a stream
 
 POSITION (S)
-    The position of the stream has been updated
+    The position of the stream has been updated. Sent to the client after all
+    missing updates for a stream have been sent to the client and they're now
+    up to date.
 
 ERROR (S, C)
     There was an error
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 586dddb40b..914cd24b55 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -54,7 +54,6 @@ class ReplicationClientFactory(ReconnectingClientFactory):
 
     def buildProtocol(self, addr):
         logger.info("Connected to replication: %r", addr)
-        self.resetDelay()
         return ClientReplicationStreamProtocol(
             self.client_name, self.server_name, self._clock, self.handler
         )
@@ -90,15 +89,23 @@ class ReplicationClientHandler(object):
         # Used for tests.
         self.awaiting_syncs = {}
 
+        # Set of stream names that have been subscribe to, but haven't yet
+        # caught up with. This is used to track when the client has been fully
+        # connected to the remote.
+        self.streams_connecting = None
+
+        # The factory used to create connections.
+        self.factory = None
+
     def start_replication(self, hs):
         """Helper method to start a replication connection to the remote server
         using TCP.
         """
         client_name = hs.config.worker_name
-        factory = ReplicationClientFactory(hs, client_name, self)
+        self.factory = ReplicationClientFactory(hs, client_name, self)
         host = hs.config.worker_replication_host
         port = hs.config.worker_replication_port
-        hs.get_reactor().connectTCP(host, port, factory)
+        hs.get_reactor().connectTCP(host, port, self.factory)
 
     def on_rdata(self, stream_name, token, rows):
         """Called when we get new replication data. By default this just pokes
@@ -115,6 +122,12 @@ class ReplicationClientHandler(object):
 
         Can be overriden in subclasses to handle more.
         """
+        # When we get a `POSITION` command it means we've finished getting
+        # missing updates for the given stream, and are now up to date.
+        self.streams_connecting.discard(stream_name)
+        if not self.streams_connecting:
+            self.finished_connecting()
+
         return self.store.process_replication_rows(stream_name, token, [])
 
     def on_sync(self, data):
@@ -140,6 +153,10 @@ class ReplicationClientHandler(object):
             args["account_data"] = user_account_data
         elif room_account_data:
             args["account_data"] = room_account_data
+
+        # Record which streams we're in the process of subscribing to
+        self.streams_connecting = set(args.keys())
+
         return args
 
     def get_currently_syncing_users(self):
@@ -204,3 +221,18 @@ class ReplicationClientHandler(object):
             for cmd in self.pending_commands:
                 connection.send_command(cmd)
             self.pending_commands = []
+
+            # This will happen if we don't actually subscribe to any streams
+            if not self.streams_connecting:
+                self.finished_connecting()
+
+    def finished_connecting(self):
+        """Called when we have successfully subscribed and caught up to all
+        streams we're interested in.
+        """
+        logger.info("Finished connecting to server")
+
+        # We don't reset the delay any earlier as otherwise if there is a
+        # problem during start up we'll end up tight looping connecting to the
+        # server.
+        self.factory.resetDelay()
diff --git a/synapse/replication/tcp/commands.py b/synapse/replication/tcp/commands.py
index 327556f6a1..2098c32a77 100644
--- a/synapse/replication/tcp/commands.py
+++ b/synapse/replication/tcp/commands.py
@@ -127,8 +127,11 @@ class RdataCommand(Command):
 
 
 class PositionCommand(Command):
-    """Sent by the client to tell the client the stream postition without
+    """Sent by the server to tell the client the stream postition without
     needing to send an RDATA.
+
+    Sent to the client after all missing updates for a stream have been sent
+    to the client and they're now up to date.
     """
     NAME = "POSITION"