diff --git a/README.rst b/README.rst
index 3014edaac..80e1b26e6 100644
--- a/README.rst
+++ b/README.rst
@@ -440,6 +440,10 @@ SRV record, as that is the name other machines will expect it to have::
     python -m synapse.app.homeserver --config-path homeserver.yaml
 
 
+If you've already generated the config file, you need to edit the "server_name"
+in you  ```homeserver.yaml``` file. If you've already started Synapse and a
+database has been created, you will have to recreate the database.
+
 You may additionally want to pass one or more "-v" options, in order to
 increase the verbosity of logging output; at least for initial testing.
 
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 5c2d6bfea..187edd516 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -133,6 +133,7 @@ class ServerConfig(Config):
         # The domain name of the server, with optional explicit port.
         # This is used by remote servers to connect to this server,
         # e.g. matrix.org, localhost:8080, etc.
+        # This is also the last part of your UserID.
         server_name: "%(server_name)s"
 
         # When running as a daemon, the file to store the pid in