diff --git a/dendrite-sample.yaml b/dendrite-sample.yaml
index 8abc230115..7affc25994 100644
--- a/dendrite-sample.yaml
+++ b/dendrite-sample.yaml
@@ -72,6 +72,10 @@ global:
   # The base URL to delegate client-server communications to e.g. https://localhost
   well_known_client_name: ""
 
+  # The server name to delegate sliding sync communications to, with optional port.
+  # Requires `well_known_client_name` to also be configured.
+  well_known_sliding_sync_proxy: ""
+
   # Lists of domains that the server will trust as identity servers to verify third
   # party identifiers such as phone numbers and email addresses.
   trusted_third_party_id_servers: