diff --git a/src/matrixrtc/BasicEncryptionManager.ts b/src/matrixrtc/BasicEncryptionManager.ts
index 15ce0e883..313255bc1 100644
--- a/src/matrixrtc/BasicEncryptionManager.ts
+++ b/src/matrixrtc/BasicEncryptionManager.ts
@@ -30,6 +30,8 @@ type DeviceInfo = {
     deviceId: string;
 };
 
+export type ParticipantId = string;
+
 type OutboundEncryptionSession = {
     key: Uint8Array;
     creationTS: number;
@@ -41,13 +43,11 @@ type OutboundEncryptionSession = {
 
 type InboundEncryptionSession = {
     key: Uint8Array;
-    participantId: string;
+    participantId: ParticipantId;
     keyId: number;
     creationTS: number;
 };
 
-export type ParticipantId = string;
-
 /**
  * A simple encryption manager.
  * This manager is basic becasue it will rotate the keys for any membership change.