diff --git a/src/core/ipv6/ip6_frag.c b/src/core/ipv6/ip6_frag.c
index 4dc9df31..dd385f43 100644
--- a/src/core/ipv6/ip6_frag.c
+++ b/src/core/ipv6/ip6_frag.c
@@ -336,7 +336,8 @@ ip6_reass(struct pbuf *p)
 #if IPV6_FRAG_COPYHEADER
     MEMCPY(&ipr->iphdr, ip6_current_header(), IP6_HLEN);
 #else /* IPV6_FRAG_COPYHEADER */
-    ipr->iphdr = (struct ip6_hdr *)ip6_current_header();
+    /* need to use the none-const pointer here: */
+    ipr->iphdr = ip_data.current_ip6_header;
 #endif /* IPV6_FRAG_COPYHEADER */
 
     /* copy the fragmented packet id. */
@@ -475,7 +476,8 @@ ip6_reass(struct pbuf *p)
       MEMCPY(&ipr->iphdr, ip6_current_header(), IP6_HLEN);
     }
 #else /* IPV6_FRAG_COPYHEADER */
-    ipr->iphdr = (struct ip6_hdr *)ip6_current_header();
+    /* need to use the none-const pointer here: */
+    ipr->iphdr = ip_data.current_ip6_header;
 #endif /* IPV6_FRAG_COPYHEADER */
   }
 
diff --git a/src/include/lwip/ip.h b/src/include/lwip/ip.h
index 972546e0..5f439d6b 100644
--- a/src/include/lwip/ip.h
+++ b/src/include/lwip/ip.h
@@ -131,11 +131,11 @@ struct ip_globals
   struct netif *current_input_netif;
 #if LWIP_IPV4
   /** Header of the input packet currently being processed. */
-  const struct ip_hdr *current_ip4_header;
+  struct ip_hdr *current_ip4_header;
 #endif /* LWIP_IPV4 */
 #if LWIP_IPV6
   /** Header of the input IPv6 packet currently being processed. */
-  const struct ip6_hdr *current_ip6_header;
+  struct ip6_hdr *current_ip6_header;
 #endif /* LWIP_IPV6 */
   /** Total header length of current_ip4/6_header (i.e. after this, the UDP/TCP header starts) */
   u16_t current_ip_header_tot_len;
@@ -167,11 +167,11 @@ extern struct ip_globals ip_data;
 /** Get the IPv4 header of the current packet.
  * This function must only be called from a receive callback (udp_recv,
  * raw_recv, tcp_accept). It will return NULL otherwise. */
-#define ip4_current_header()     (ip_data.current_ip4_header)
+#define ip4_current_header()     ((const struct ip_hdr*)(ip_data.current_ip4_header))
 /** Get the IPv6 header of the current packet.
  * This function must only be called from a receive callback (udp_recv,
  * raw_recv, tcp_accept). It will return NULL otherwise. */
-#define ip6_current_header()      (ip_data.current_ip6_header)
+#define ip6_current_header()      ((const struct ip6_hdr*)(ip_data.current_ip6_header))
 /** Returns TRUE if the current IP input packet is IPv6, FALSE if it is IPv4 */
 #define ip_current_is_v6()        (ip6_current_header() != NULL)
 /** Source IPv6 address of current_header */
@@ -183,8 +183,8 @@ extern struct ip_globals ip_data;
                                    IP6H_NEXTH(ip6_current_header()) :\
                                    IPH_PROTO(ip4_current_header()))
 /** Get the transport layer header */
-#define ip_next_header_ptr()     ((void*)((ip_current_is_v6() ? \
-  (u8_t*)ip6_current_header() : (u8_t*)ip4_current_header())  + ip_current_header_tot_len()))
+#define ip_next_header_ptr()     ((const void*)((ip_current_is_v6() ? \
+  (const u8_t*)ip6_current_header() : (const u8_t*)ip4_current_header())  + ip_current_header_tot_len()))
 
 /** Set an IP_PCB to IPv6 (IPv4 is the default) */
 #define ip_set_v6(pcb, val)       do{if(pcb != NULL) { pcb->isipv6 = val; }}while(0)
@@ -199,13 +199,13 @@ extern struct ip_globals ip_data;
 /** Get the IPv4 header of the current packet.
  * This function must only be called from a receive callback (udp_recv,
  * raw_recv, tcp_accept). It will return NULL otherwise. */
-#define ip4_current_header()     (ip_data.current_ip4_header)
+#define ip4_current_header()     ((const struct ip_hdr*)(ip_data.current_ip4_header))
 /** Always returns FALSE when only supporting IPv4 only */
 #define ip_current_is_v6()        0
 /** Get the transport layer protocol */
 #define ip_current_header_proto() IPH_PROTO(ip4_current_header())
 /** Get the transport layer header */
-#define ip_next_header_ptr()     ((void*)((u8_t*)ip4_current_header() + ip_current_header_tot_len()))
+#define ip_next_header_ptr()     ((const void*)((const u8_t*)ip4_current_header() + ip_current_header_tot_len()))
 /** Source IP4 address of current_header */
 #define ip4_current_src_addr()     (&ip_data.current_iphdr_src)
 /** Destination IP4 address of current_header */
@@ -216,13 +216,13 @@ extern struct ip_globals ip_data;
 /** Get the IPv6 header of the current packet.
  * This function must only be called from a receive callback (udp_recv,
  * raw_recv, tcp_accept). It will return NULL otherwise. */
-#define ip6_current_header()      (ip_data.current_ip6_header)
+#define ip6_current_header()      ((const struct ip6_hdr*)(ip_data.current_ip6_header))
 /** Always returns TRUE when only supporting IPv6 only */
 #define ip_current_is_v6()        1
 /** Get the transport layer protocol */
 #define ip_current_header_proto() IP6H_NEXTH(ip6_current_header())
 /** Get the transport layer header */
-#define ip_next_header_ptr()     ((void*)((u8_t*)ip6_current_header()))
+#define ip_next_header_ptr()     ((const void*)((const u8_t*)ip6_current_header()))
 /** Source IP6 address of current_header */
 #define ip6_current_src_addr()    (&ip_data.current_iphdr_src)
 /** Destination IP6 address of current_header */