diff --git a/27.md b/27.md
index 4954f3b..a0e9d9b 100644
--- a/27.md
+++ b/27.md
@@ -77,6 +77,7 @@ up to date. Both would construct the following message to subscribe:
 6. Live events can take advantage of ephemeral events and previously-shared multicast group for communication during the event.
 7. Smart contracts may communicate in privacy-preserving way with individual clients using unique short-lived multicast groups.
 8. Clients interested in Bitcoin prices in USD may subscribe to the multicast group "prices:btc:usd". Many providers may publish their events to the same multicast groups.
+9. Testnet-like multicast group for debugging in Nostr.
 
 # Notes