diff --git a/Mailbox-Properties-Client.md b/Mailbox-Properties-Client.md
index 8903bf0..57ac943 100644
--- a/Mailbox-Properties-Client.md
+++ b/Mailbox-Properties-Client.md
@@ -17,7 +17,7 @@ The client uses a separate BSP group for communicating with each contact. The [g
 
 For major version 0, the `properties` of a well-formed update are either 0 (empty dict), which means for the receiver that there is no mailbox available. Or, there are precisely 4 items:
 
-* "onionPubKey" : byte[32] -- v3 Onion Service public key of the mailbox (Onion Address is derived from this)
+* "onionAddress" : String -- Onion Address of mailbox (derived from v3 Onion Service public key, 56 lower-case base32 chars)
 * "token" : byte[32] -- token used for authenticating with the mailbox
 * "inboxId" : byte[32] -- folder id used when receiving data from the mailbox
 * "outboxId" : byte[32] -- folder id used when delivering data to the mailbox