diff --git a/src/handle_packets.c b/src/handle_packets.c
index 2606499..bddce3a 100644
--- a/src/handle_packets.c
+++ b/src/handle_packets.c
@@ -57,6 +57,10 @@ static inline struct SwiftNetPacketQueueNode* construct_node(const uint32_t data
     return node;
 }
 
+static inline bool valid_ip_header(const struct SwiftNetNetworkData* restrict const network_data, const struct ReceiverPacketData* const restrict packet_data) {
+    return ip_checksum(packet_data->data + GET_PREPEND_SIZE(network_data)) == 0;
+}
+
 static inline void swiftnet_handle_packets(
 	struct SwiftNetPacketQueue* const packet_queue,
     pthread_mutex_t* const process_packets_mtx,
@@ -73,6 +77,10 @@ static inline void swiftnet_handle_packets(
 
     addr_type = GET_ADDR_TYPE(network_data);
 
+    if (!valid_ip_header(network_data, &packet_data)) {
+        goto exit;   
+    }
+
     if (unlikely(packet_data.data_len == 0)) {
         goto exit;
     }
diff --git a/src/internal/internal.h b/src/internal/internal.h
index d34efee..eefc060 100644
--- a/src/internal/internal.h
+++ b/src/internal/internal.h
@@ -230,6 +230,20 @@ CRC_TARGET MAYBE_UNUSED static uint32_t crc32(const uint8_t* const data, const u
 
     return ~crc;
 }
+
+static uint16_t ip_checksum(const uint8_t* header) {
+    uint32_t sum = 0;
+
+    for(uint16_t i = 0; i < 20; i+=2) {
+        sum += (uint16_t)((header[0] << 8u) | header[1]);   // big-endian 16-bit word
+        header += 2;
+    }
+
+    while (sum >> 16) sum = (sum & 0xFFFF) + (sum >> 16);
+
+    return (uint16_t)~sum;
+}
+
 enum StackCreatingState {
     STACK_CREATING_LOCKED = 0,
     STACK_CREATING_UNLOCKED = 1
diff --git a/src/internal/networking.h b/src/internal/networking.h
index 3b92620..72a53f7 100644
--- a/src/internal/networking.h
+++ b/src/internal/networking.h
@@ -15,8 +15,10 @@
     // Simple crc16 call with proper memory order
     #define HANDLE_CHECKSUM(buffer, size, network_data, packet_metadata) \
         { \
+        const uint16_t ip_sum = htons(ip_checksum(buffer + GET_PREPEND_SIZE(network_data))); \
         const uint32_t checksum = crc32(buffer + GET_PREPEND_SIZE(network_data) + sizeof(struct ip), size + sizeof(struct SwiftNetChunkMetadata) + (packet_metadata ? sizeof(struct SwiftNetPacketMetadata) : 0)); \
         memcpy(buffer + GET_PREPEND_SIZE(network_data) + sizeof(struct ip) + offsetof(struct SwiftNetChunkMetadata, checksum), &checksum, sizeof(checksum)); \
+        memcpy(buffer + GET_PREPEND_SIZE(network_data) + offsetof(struct ip, ip_sum), &ip_sum, SIZEOF_FIELD(struct ip, ip_sum)); \
         }
 
     #define GET_ADDR_TYPE(network_data) (network_data)->addr_type
@@ -91,8 +93,10 @@
 
     #define HANDLE_CHECKSUM(buffer, size, network_data, packet_metadata) \
         { \
+            const uint16_t ip_sum = htons(ip_checksum(buffer + GET_PREPEND_SIZE(network_data))); \
             const uint32_t checksum = crc32(buffer + GET_PREPEND_SIZE(network_data) + sizeof(struct ip), size + sizeof(struct SwiftNetChunkMetadata) + (packet_metadata ? sizeof(struct SwiftNetPacketMetadata) : 0)); \
             memcpy(buffer + GET_PREPEND_SIZE(network_data) + sizeof(struct ip) + offsetof(struct SwiftNetChunkMetadata, checksum), &checksum, sizeof(checksum)); \
+            memcpy(buffer + GET_PREPEND_SIZE(network_data) + offsetof(struct ip, ip_sum), &ip_sum, SIZEOF_FIELD(struct ip, ip_sum)); \
         }
 
     #define GET_ADDR_TYPE(network_data) (network_data)->addr_type