diff --git a/internal/handshake/tls_extension.go b/internal/handshake/tls_extension.go
index e40ec3dee..9f0488e43 100644
--- a/internal/handshake/tls_extension.go
+++ b/internal/handshake/tls_extension.go
@@ -6,7 +6,7 @@ import (
 
 type transportParameterID uint16
 
-const quicTLSExtensionType = 26
+const quicTLSExtensionType = 0xff5
 
 const (
 	initialMaxStreamDataParameterID  transportParameterID = 0x0