diff --git a/packages/interface-pubsub/src/index.ts b/packages/interface-pubsub/src/index.ts
index 10b1c5121..651a8eb0b 100644
--- a/packages/interface-pubsub/src/index.ts
+++ b/packages/interface-pubsub/src/index.ts
@@ -27,15 +27,22 @@ export const StrictNoSign = 'StrictNoSign'
 
 export type SignaturePolicy = typeof StrictSign | typeof StrictNoSign
 
-export interface Message {
+export interface StrictSignMessage {
   from: PeerId
   topic: string
   data: Uint8Array
-  sequenceNumber?: bigint
-  signature?: Uint8Array
-  key?: Uint8Array
+  sequenceNumber: bigint
+  signature: Uint8Array
+  key: Uint8Array
 }
 
+export interface StrictNoSignMessage {
+  topic: string
+  data: Uint8Array
+}
+
+export type Message = StrictSignMessage | StrictNoSignMessage
+
 export interface PubSubRPCMessage {
   from?: Uint8Array
   topic?: string