diff --git a/include/transport/protocol.proto b/include/transport/protocol.proto
index 8f8a790b99ff69b6a9651b9d9c7e5ca52968b3ae..744426003ef0987f32896aae76f311699770f6be 100644
--- a/include/transport/protocol.proto
+++ b/include/transport/protocol.proto
@@ -77,6 +77,7 @@ message ConversationMessage {
 	optional bool headline = 7;
 	optional string id = 8;
 	optional bool pm = 9;
+	optional bool carbon = 10;
 }
 
 message Room {