diff --git a/bacnet-stack/ports/atmega168/dlmstp.c b/bacnet-stack/ports/atmega168/dlmstp.c
index d7034301..9fc4453e 100644
--- a/bacnet-stack/ports/atmega168/dlmstp.c
+++ b/bacnet-stack/ports/atmega168/dlmstp.c
@@ -43,6 +43,7 @@
 #include "npdu.h"
 #include "bits.h"
 #include "bacaddr.h"
+/* special optimization - I-Am response in this module */
 #include "iam.h"
 #include "txbuf.h"