diff --git a/src/transport.h b/src/transport.h
index e7ddd4e07..5d4f586f8 100644
--- a/src/transport.h
+++ b/src/transport.h
@@ -25,6 +25,7 @@ typedef enum _PEP_transport_id {
     PEP_trans_auto = 0,
 //    PEP_trans_Email = 0x01,
 //    PEP_trans_RCE = 0x02,
+//    PEP_trans_PDL = 0x03,
 
     PEP_trans__count,
     PEP_trans_CC = 0xfe