diff --git a/src/core/ipv4/ip.c b/src/core/ipv4/ip.c
index fcca17c6..e780175d 100644
--- a/src/core/ipv4/ip.c
+++ b/src/core/ipv4/ip.c
@@ -597,7 +597,7 @@ err_t ip_output_if_opt(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
     IPH_TTL_SET(iphdr, ttl);
     IPH_PROTO_SET(iphdr, proto);
 #if CHECKSUM_GEN_IP_INLINE
-    chk_sum = (proto << 8) | ttl;
+    chk_sum = LWIP_MAKE_U16(proto, ttl);
 #endif /* CHECKSUM_GEN_IP_INLINE */
 
     /* dest cannot be NULL here */
diff --git a/src/include/lwip/def.h b/src/include/lwip/def.h
index b500af2c..52d511af 100644
--- a/src/include/lwip/def.h
+++ b/src/include/lwip/def.h
@@ -47,6 +47,12 @@ extern "C" {
 #define NULL ((void *)0)
 #endif
 
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define LWIP_MAKE_U16(a, b) ((a << 8) | b)
+#else
+#define LWIP_MAKE_U16(a, b) ((b << 8) | a)
+#endif 
+
 #ifdef htons
 #undef htons
 #endif /* htons */