diff --git a/changelog.d/4929.misc b/changelog.d/4929.misc
new file mode 100644
index 0000000000..aaf02078b9
--- /dev/null
+++ b/changelog.d/4929.misc
@@ -0,0 +1 @@
+Fix `ClientReplicationStreamProtocol.__str__()`.
diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py
index e16fad5261..02e5bf6cc8 100644
--- a/synapse/replication/tcp/protocol.py
+++ b/synapse/replication/tcp/protocol.py
@@ -375,8 +375,11 @@ class BaseReplicationStreamProtocol(LineOnlyReceiver):
             self.transport.unregisterProducer()
 
     def __str__(self):
+        addr = None
+        if self.transport:
+            addr = str(self.transport.getPeer())
         return "ReplicationConnection<name=%s,conn_id=%s,addr=%s>" % (
-            self.name, self.conn_id, self.addr,
+            self.name, self.conn_id, addr,
         )
 
     def id(self):
@@ -392,12 +395,11 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
     VALID_INBOUND_COMMANDS = VALID_CLIENT_COMMANDS
     VALID_OUTBOUND_COMMANDS = VALID_SERVER_COMMANDS
 
-    def __init__(self, server_name, clock, streamer, addr):
+    def __init__(self, server_name, clock, streamer):
         BaseReplicationStreamProtocol.__init__(self, clock)  # Old style class
 
         self.server_name = server_name
         self.streamer = streamer
-        self.addr = addr
 
         # The streams the client has subscribed to and is up to date with
         self.replication_streams = set()
diff --git a/synapse/replication/tcp/resource.py b/synapse/replication/tcp/resource.py
index 47cdf30bd3..7fc346c7b6 100644
--- a/synapse/replication/tcp/resource.py
+++ b/synapse/replication/tcp/resource.py
@@ -57,7 +57,6 @@ class ReplicationStreamProtocolFactory(Factory):
             self.server_name,
             self.clock,
             self.streamer,
-            addr
         )