diff --git a/src/core/def.c b/src/core/def.c
index 305fe0f2..35f142c7 100644
--- a/src/core/def.c
+++ b/src/core/def.c
@@ -218,7 +218,7 @@ lwip_itoa(char* result, size_t bufsize, int number)
      it will get */
   tmp = &result[bufsize-2];
   while ((n != 0) && (result_len < (bufsize - 1))) {
-    char val = '0' + (n % 10);
+    char val = (char)('0' + (n % 10));
     *tmp = val;
     tmp--;
     n = n / 10;
diff --git a/src/core/inet_chksum.c b/src/core/inet_chksum.c
index 917f3e4f..646074c6 100644
--- a/src/core/inet_chksum.c
+++ b/src/core/inet_chksum.c
@@ -260,7 +260,7 @@ static u16_t
 inet_cksum_pseudo_base(struct pbuf *p, u8_t proto, u16_t proto_len, u32_t acc)
 {
   struct pbuf *q;
-  u8_t swapped = 0;
+  int swapped = 0;
 
   /* iterate through all pbuf in chain */
   for (q = p; q != NULL; q = q->next) {
@@ -272,7 +272,7 @@ inet_cksum_pseudo_base(struct pbuf *p, u8_t proto, u16_t proto_len, u32_t acc)
        to check whether we really need to execute it, and does no harm */
     acc = FOLD_U32T(acc);
     if (q->len % 2 != 0) {
-      swapped = 1 - swapped;
+      swapped = !swapped;
       acc = SWAP_BYTES_IN_WORD(acc);
     }
     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
@@ -400,7 +400,7 @@ inet_cksum_pseudo_partial_base(struct pbuf *p, u8_t proto, u16_t proto_len,
        u16_t chksum_len, u32_t acc)
 {
   struct pbuf *q;
-  u8_t swapped = 0;
+  int swapped = 0;
   u16_t chklen;
 
   /* iterate through all pbuf in chain */
@@ -412,13 +412,13 @@ inet_cksum_pseudo_partial_base(struct pbuf *p, u8_t proto, u16_t proto_len,
       chklen = chksum_len;
     }
     acc += LWIP_CHKSUM(q->payload, chklen);
-    chksum_len -= chklen;
+    chksum_len = (u16_t)(chksum_len - chklen);
     LWIP_ASSERT("delete me", chksum_len < 0x7fff);
     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
     /* fold the upper bit down */
     acc = FOLD_U32T(acc);
     if (q->len % 2 != 0) {
-      swapped = 1 - swapped;
+      swapped = !swapped;
       acc = SWAP_BYTES_IN_WORD(acc);
     }
     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
@@ -569,15 +569,14 @@ inet_chksum_pbuf(struct pbuf *p)
 {
   u32_t acc;
   struct pbuf *q;
-  u8_t swapped;
+  int swapped = 0;
 
   acc = 0;
-  swapped = 0;
   for (q = p; q != NULL; q = q->next) {
     acc += LWIP_CHKSUM(q->payload, q->len);
     acc = FOLD_U32T(acc);
     if (q->len % 2 != 0) {
-      swapped = 1 - swapped;
+      swapped = !swapped;
       acc = SWAP_BYTES_IN_WORD(acc);
     }
   }