diff --git a/event_registration.md b/event_registration.md
index 03f23b9..f0c47ca 100644
--- a/event_registration.md
+++ b/event_registration.md
@@ -63,7 +63,8 @@ message QRCodePayload {
   uint32 version = 1;
   TraceLocation locationData = 2;
   CrowdNotifierData crowdNotifierData = 3;
-  CWALocationData vendorData = 4;
+  // byte sequence of CWALocationData
+  bytes vendorData = 4;
 }
 
 message TraceLocation {