diff --git a/bacnet-stack/include/dlmstp.h b/bacnet-stack/include/dlmstp.h
index 77572aaf..7feb1cbf 100644
--- a/bacnet-stack/include/dlmstp.h
+++ b/bacnet-stack/include/dlmstp.h
@@ -42,7 +42,7 @@
 #include "npdu.h"
 
 /* defines specific to MS/TP */
-#define MAX_HEADER (2+1+1+1+2+1+2+1)
+#define MAX_HEADER (2+1+1+1+2+1)
 #define MAX_MPDU (MAX_HEADER+MAX_PDU)
 
 typedef struct dlmstp_packet {
diff --git a/bacnet-stack/ports/pic18f6720/dlmstp.h b/bacnet-stack/ports/pic18f6720/dlmstp.h
index ea316090..418d7d34 100644
--- a/bacnet-stack/ports/pic18f6720/dlmstp.h
+++ b/bacnet-stack/ports/pic18f6720/dlmstp.h
@@ -42,7 +42,7 @@
 #include "npdu.h"
 
 /* defines specific to MS/TP */
-#define MAX_HEADER (2+1+1+1+2+1+2+1)
+#define MAX_HEADER (2+1+1+1+2+1)
 #define MAX_MPDU (MAX_HEADER+MAX_PDU)
 
 typedef struct dlmstp_packet {