diff --git a/ts/sio-interfaces.data.ts b/ts/sio-interfaces.data.ts
index 020eed8..42a91f2 100644
--- a/ts/sio-interfaces.data.ts
+++ b/ts/sio-interfaces.data.ts
@@ -13,6 +13,7 @@ export interface ISioConversationBlock {
 }
 
 export interface ISioConversation {
+  subject: string;
   parties: ISioConversationParty[];
   conversationBlocks: ISioConversationBlock[];
 }