diff --git a/src/core/def.c b/src/core/def.c
index 35f142c7..d3004d4d 100644
--- a/src/core/def.c
+++ b/src/core/def.c
@@ -75,7 +75,7 @@
 u16_t
 lwip_htons(u16_t n)
 {
-  return (u16_t)PP_HTONS(n);
+  return PP_HTONS(n);
 }
 #endif /* lwip_htons */
 
@@ -89,7 +89,7 @@ lwip_htons(u16_t n)
 u32_t
 lwip_htonl(u32_t n)
 {
-  return (u32_t)PP_HTONL(n);
+  return PP_HTONL(n);
 }
 #endif /* lwip_htonl */
 
diff --git a/src/core/ipv4/icmp.c b/src/core/ipv4/icmp.c
index 5ee24eed..c866663b 100644
--- a/src/core/ipv4/icmp.c
+++ b/src/core/ipv4/icmp.c
@@ -92,7 +92,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
   MIB2_STATS_INC(mib2.icmpinmsgs);
 
   iphdr_in = ip4_current_header();
-  hlen = IPH_HL(iphdr_in) * 4;
+  hlen = IPH_HL_BYTES(iphdr_in);
   if (hlen < IP_HLEN) {
     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short IP header (%"S16_F" bytes) received\n", hlen));
     goto lenerr;
@@ -157,8 +157,13 @@ icmp_input(struct pbuf *p, struct netif *inp)
        * allocate a new one and copy p into it
        */
       struct pbuf *r;
+      u16_t alloc_len = (u16_t)(p->tot_len + hlen);
+      if (alloc_len < p->tot_len) {
+        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed (tot_len overflow)\n"));
+        goto icmperr;
+      }
       /* allocate new packet buffer with space for link headers */
-      r = pbuf_alloc(PBUF_LINK, p->tot_len + hlen, PBUF_RAM);
+      r = pbuf_alloc(PBUF_LINK, alloc_len, PBUF_RAM);
       if (r == NULL) {
         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
         goto icmperr;
@@ -188,7 +193,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
       p = r;
     } else {
       /* restore p->payload to point to icmp header (cannot fail) */
-      if (pbuf_header(p, -(s16_t)(hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
+      if (pbuf_header(p, (s16_t)-(s16_t)(hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
         LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
         goto icmperr;
       }
@@ -210,9 +215,9 @@ icmp_input(struct pbuf *p, struct netif *inp)
       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP) {
         /* adjust the checksum */
         if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
-          iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
+          iecho->chksum = (u16_t)(iecho->chksum + PP_HTONS((u16_t)(ICMP_ECHO << 8)) + 1);
         } else {
-          iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
+          iecho->chksum = (u16_t)(iecho->chksum + PP_HTONS(ICMP_ECHO << 8));
         }
       }
 #if LWIP_CHECKSUM_CTRL_PER_NETIF
diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index ee98b062..a77a3c32 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -684,7 +684,7 @@ static void
 igmp_start_timer(struct igmp_group *group, u8_t max_time)
 {
 #ifdef LWIP_RAND
-  group->timer = max_time > 2 ? (LWIP_RAND() % max_time) : 1;
+  group->timer = (u16_t)(max_time > 2 ? (LWIP_RAND() % max_time) : 1);
 #else /* LWIP_RAND */
   /* ATTENTION: use this only if absolutely necessary! */
   group->timer = max_time / 2;
diff --git a/src/core/netif.c b/src/core/netif.c
index e642a950..19348ec6 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -1353,7 +1353,7 @@ netif_create_ip6_linklocal_address(struct netif *netif, u8_t from_mac_48bit)
         ((u32_t)(netif->hwaddr[1]) << 16) |
         ((u32_t)(netif->hwaddr[2]) << 8) |
         (0xff));
-    ip_2_ip6(&netif->ip6_addr[0])->addr[3] = lwip_htonl((0xfeul << 24) |
+    ip_2_ip6(&netif->ip6_addr[0])->addr[3] = lwip_htonl((u32_t)(0xfeul << 24) |
         ((u32_t)(netif->hwaddr[3]) << 16) |
         ((u32_t)(netif->hwaddr[4]) << 8) |
         (netif->hwaddr[5]));
diff --git a/src/include/lwip/def.h b/src/include/lwip/def.h
index 82a9d896..f836ba90 100644
--- a/src/include/lwip/def.h
+++ b/src/include/lwip/def.h
@@ -94,12 +94,12 @@ u32_t lwip_htonl(u32_t x);
 /* These macros should be calculated by the preprocessor and are used
    with compile-time constants only (so that there is no little-endian
    overhead at runtime). */
-#define PP_HTONS(x) ((((x) & 0x00ffUL) << 8) | (((x) & 0xff00UL) >> 8))
+#define PP_HTONS(x) ((u16_t)((((x) & (u16_t)0x00ffU) << 8) | (((x) & (u16_t)0xff00U) >> 8)))
 #define PP_NTOHS(x) PP_HTONS(x)
-#define PP_HTONL(x) ((((x) & 0x000000ffUL) << 24) | \
-                     (((x) & 0x0000ff00UL) <<  8) | \
-                     (((x) & 0x00ff0000UL) >>  8) | \
-                     (((x) & 0xff000000UL) >> 24))
+#define PP_HTONL(x) ((((x) & (u32_t)0x000000ffUL) << 24) | \
+                     (((x) & (u32_t)0x0000ff00UL) <<  8) | \
+                     (((x) & (u32_t)0x00ff0000UL) >>  8) | \
+                     (((x) & (u32_t)0xff000000UL) >> 24))
 #define PP_NTOHL(x) PP_HTONL(x)
 #endif /* BYTE_ORDER == BIG_ENDIAN */
 
diff --git a/src/include/lwip/prot/ip4.h b/src/include/lwip/prot/ip4.h
index bd442c68..7eb4201d 100644
--- a/src/include/lwip/prot/ip4.h
+++ b/src/include/lwip/prot/ip4.h
@@ -101,6 +101,7 @@ PACK_STRUCT_END
 /* Macros to get struct ip_hdr fields: */
 #define IPH_V(hdr)  ((hdr)->_v_hl >> 4)
 #define IPH_HL(hdr) ((hdr)->_v_hl & 0x0f)
+#define IPH_HL_BYTES(hdr) ((u8_t)(IPH_HL(hdr) * 4))
 #define IPH_TOS(hdr) ((hdr)->_tos)
 #define IPH_LEN(hdr) ((hdr)->_len)
 #define IPH_ID(hdr) ((hdr)->_id)