diff --git a/apps/router-ipv6/main.c b/apps/router-ipv6/main.c
index c4871cc5..46a5b629 100644
--- a/apps/router-ipv6/main.c
+++ b/apps/router-ipv6/main.c
@@ -56,8 +56,6 @@
 #include "bacnet/datalink/bvlc6.h"
 #include "bacnet/datalink/bip6.h"
 #include "bacnet/basic/bbmd6/h_bbmd6.h"
-#undef MAX_HEADER
-#undef MAX_MPDU
 #include "bacnet/datalink/bip.h"
 #include "bacnet/datalink/bvlc.h"
 #include "bacnet/basic/bbmd/h_bbmd.h"
diff --git a/apps/router-mstp/main.c b/apps/router-mstp/main.c
index 82dd7a92..89f45a45 100644
--- a/apps/router-mstp/main.c
+++ b/apps/router-mstp/main.c
@@ -54,8 +54,6 @@
 #include "bacport.h"
 /* our datalink layers */
 #include "bacnet/datalink/dlmstp.h"
-#undef MAX_HEADER
-#undef MAX_MPDU
 #include "bacnet/datalink/bip.h"
 #include "bacnet/datalink/bvlc.h"
 #include "bacnet/basic/bbmd/h_bbmd.h"
diff --git a/ports/win32/dlmstp-mm.c b/ports/win32/dlmstp-mm.c
index a1ca61b1..284780a3 100644
--- a/ports/win32/dlmstp-mm.c
+++ b/ports/win32/dlmstp-mm.c
@@ -126,7 +126,7 @@ int dlmstp_send_pdu(BACNET_ADDRESS *dest, /* destination address */
             Transmit_Packet.pdu[i] = pdu[i];
         }
         bacnet_address_copy(&Transmit_Packet.address, dest);
-        bytes_sent = pdu_len + MAX_HEADER;
+        bytes_sent = pdu_len + DLMSTP_HEADER_MAX;
         Transmit_Packet.ready = true;
     }
 
@@ -282,7 +282,7 @@ uint16_t MSTP_Get_Send(
     } else {
         destination = MSTP_BROADCAST_ADDRESS;
     }
-    if ((MAX_HEADER + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
+    if ((DLMSTP_HEADER_MAX + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
         return 0;
     }
     /* convert the PDU into the MSTP Frame */
@@ -421,7 +421,7 @@ uint16_t MSTP_Get_Reply(
     } else {
         return 0;
     }
-    if ((MAX_HEADER + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
+    if ((DLMSTP_HEADER_MAX + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
         return 0;
     }
     /* is this the reply to the DER? */
diff --git a/ports/win32/dlmstp.c b/ports/win32/dlmstp.c
index 80d608c6..8fccf21c 100644
--- a/ports/win32/dlmstp.c
+++ b/ports/win32/dlmstp.c
@@ -111,7 +111,7 @@ int dlmstp_send_pdu(BACNET_ADDRESS *dest, /* destination address */
             Transmit_Packet.pdu[i] = pdu[i];
         }
         bacnet_address_copy(&Transmit_Packet.address, dest);
-        bytes_sent = pdu_len + MAX_HEADER;
+        bytes_sent = pdu_len + DLMSTP_HEADER_MAX;
         Transmit_Packet.ready = true;
     }
 
@@ -267,7 +267,7 @@ uint16_t MSTP_Get_Send(
     } else {
         destination = MSTP_BROADCAST_ADDRESS;
     }
-    if ((MAX_HEADER + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
+    if ((DLMSTP_HEADER_MAX + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
         return 0;
     }
     /* convert the PDU into the MSTP Frame */
@@ -407,7 +407,7 @@ uint16_t MSTP_Get_Reply(
     } else {
         return 0;
     }
-    if ((MAX_HEADER + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
+    if ((DLMSTP_HEADER_MAX + Transmit_Packet.pdu_len) > DLMSTP_MPDU_MAX) {
         return 0;
     }
     /* is this the reply to the DER? */