diff --git a/net/checksum.c b/net/checksum.c
index 5cb8b2c368..dabd290c64 100644
--- a/net/checksum.c
+++ b/net/checksum.c
@@ -61,6 +61,7 @@ void net_checksum_calculate(uint8_t *data, int length)
 {
     int mac_hdr_len, ip_len;
     struct ip_header *ip;
+    uint16_t csum;
 
     /*
      * Note: We cannot assume "data" is aligned, so the all code uses
@@ -106,6 +107,11 @@ void net_checksum_calculate(uint8_t *data, int length)
         return; /* not IPv4 */
     }
 
+    /* Calculate IP checksum */
+    stw_he_p(&ip->ip_sum, 0);
+    csum = net_raw_checksum((uint8_t *)ip, IP_HDR_GET_LEN(ip));
+    stw_be_p(&ip->ip_sum, csum);
+
     if (IP4_IS_FRAGMENT(ip)) {
         return; /* a fragmented IP packet */
     }
@@ -122,7 +128,6 @@ void net_checksum_calculate(uint8_t *data, int length)
     switch (ip->ip_p) {
     case IP_PROTO_TCP:
     {
-        uint16_t csum;
         tcp_header *tcp = (tcp_header *)(ip + 1);
 
         if (ip_len < sizeof(tcp_header)) {
@@ -143,7 +148,6 @@ void net_checksum_calculate(uint8_t *data, int length)
     }
     case IP_PROTO_UDP:
     {
-        uint16_t csum;
         udp_header *udp = (udp_header *)(ip + 1);
 
         if (ip_len < sizeof(udp_header)) {