diff --git a/src/core/inet.c b/src/core/inet.c
index d87065e1..59c80ea4 100644
--- a/src/core/inet.c
+++ b/src/core/inet.c
@@ -46,10 +46,21 @@
 #include "lwip/def.h"
 #include "lwip/inet.h"
 
+#include "lwip/sys.h"
 
+/* This is a reference implementation of the checksum algorithm
 
+ - it may not work on all architectures, and all processors, particularly
+   if they have issues with alignment and 16 bit access.
+
+ - in this case you will need to port it to your architecture and 
+   #define LWIP_CHKSUM <your_checksum_routine> 
+   in your sys_arch.h
+*/
+#ifndef LWIP_CHKSUM
+#define LWIP_CHKSUM lwip_standard_chksum
 static u16_t
-lwip_chksum(void *dataptr, int len)
+lwip_standard_chksum(void *dataptr, int len)
 {
   u32_t acc;
 
@@ -75,6 +86,7 @@ lwip_chksum(void *dataptr, int len)
 
   return (u16_t)acc;
 }
+#endif
 
 /* inet_chksum_pseudo:
  *
@@ -96,7 +108,7 @@ inet_chksum_pseudo(struct pbuf *p,
   for(q = p; q != NULL; q = q->next) {
     LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
       (void *)q, (void *)q->next));
-    acc += lwip_chksum(q->payload, q->len);
+    acc += LWIP_CHKSUM(q->payload, q->len);
     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%lx \n", acc));*/
     while (acc >> 16) {
       acc = (acc & 0xffffUL) + (acc >> 16);
@@ -136,7 +148,7 @@ inet_chksum(void *dataptr, u16_t len)
 {
   u32_t acc;
 
-  acc = lwip_chksum(dataptr, len);
+  acc = LWIP_CHKSUM(dataptr, len);
   while (acc >> 16) {
     acc = (acc & 0xffff) + (acc >> 16);
   }
@@ -153,7 +165,7 @@ inet_chksum_pbuf(struct pbuf *p)
   acc = 0;
   swapped = 0;
   for(q = p; q != NULL; q = q->next) {
-    acc += lwip_chksum(q->payload, q->len);
+    acc += LWIP_CHKSUM(q->payload, q->len);
     while (acc >> 16) {
       acc = (acc & 0xffffUL) + (acc >> 16);
     }