diff --git a/kernel/src/net/tcp_layer.cpp b/kernel/src/net/tcp_layer.cpp
index 1361be9e..edfd76e1 100644
--- a/kernel/src/net/tcp_layer.cpp
+++ b/kernel/src/net/tcp_layer.cpp
@@ -65,9 +65,9 @@ network::connection_handler<tcp_connection> connections;
 
 void compute_checksum(network::ethernet::packet& packet) {
     auto* ip_header  = reinterpret_cast<network::ip::header*>(packet.payload + packet.tag(1));
-    auto* tcp_header = reinterpret_cast<network::tcp::header*>(packet.payload + packet.index);
+    auto* tcp_header = reinterpret_cast<network::tcp::header*>(packet.payload + packet.tag(2));
 
-    auto tcp_len = switch_endian_16(ip_header->total_len) - sizeof(network::ip::header);
+    auto tcp_len = switch_endian_16(ip_header->total_len) - (ip_header->version_ihl & 0xF) * 4;
 
     tcp_header->checksum = 0;
 
@@ -87,10 +87,12 @@ void compute_checksum(network::ethernet::packet& packet) {
     tcp_header->checksum = switch_endian_16(network::checksum_finalize_nz(sum));
 }
 
+constexpr size_t default_tcp_header_length = 20;
+
 uint16_t get_default_flags() {
     uint16_t flags = 0; // By default
 
-    (flag_data_offset(&flags)) = 5; // No options
+    (flag_data_offset(&flags)) = default_tcp_header_length / 4; // No options
 
     return flags;
 }
@@ -106,7 +108,7 @@ void prepare_packet(network::ethernet::packet& packet, size_t source, size_t tar
     tcp_header->target_port = switch_endian_16(target);
     tcp_header->window_size = 1024;
 
-    packet.index += sizeof(network::tcp::header);
+    packet.index += default_tcp_header_length;
 }
 
 size_t tcp_payload_len(const network::ethernet::packet& packet){
@@ -126,7 +128,7 @@ size_t tcp_payload_len(const network::ethernet::packet& packet){
 // This is used for raw answer
 std::expected<network::ethernet::packet> kernel_prepare_packet(network::interface_descriptor& interface, network::ip::address target_ip, size_t source, size_t target, size_t payload_size) {
     // Ask the IP layer to craft a packet
-    network::ip::packet_descriptor desc{sizeof(network::tcp::header) + payload_size, target_ip, 0x06};
+    network::ip::packet_descriptor desc{payload_size + default_tcp_header_length, target_ip, 0x06};
     auto packet = network::ip::kernel_prepare_packet(interface, desc);
 
     if (packet) {
@@ -143,7 +145,7 @@ std::expected<network::ethernet::packet> kernel_prepare_packet(network::interfac
     auto server_port = connection.server_port;
 
     // Ask the IP layer to craft a packet
-    network::ip::packet_descriptor desc{sizeof(network::tcp::header) + payload_size, target_ip, 0x06};
+    network::ip::packet_descriptor desc{payload_size + default_tcp_header_length, target_ip, 0x06};
     auto packet = network::ip::kernel_prepare_packet(interface, desc);
 
     if (packet) {
@@ -160,7 +162,11 @@ std::expected<network::ethernet::packet> kernel_prepare_packet(network::interfac
 
 // finalize without waiting for ACK
 std::expected<void> finalize_packet_direct(network::interface_descriptor& interface, network::ethernet::packet& p) {
-    p.index -= sizeof(network::tcp::header);
+    auto* tcp_header = reinterpret_cast<network::tcp::header*>(p.payload + p.tag(2));
+
+    auto flags = switch_endian_16(tcp_header->flags);
+
+    p.index -= *flag_data_offset(&flags) * 4;
 
     // Compute the checksum
     compute_checksum(p);
@@ -224,7 +230,7 @@ void network::tcp::decode(network::interface_descriptor& interface, network::eth
         if (*flag_psh(&flags) && connection.socket) {
             auto& socket = *connection.socket;
 
-            packet.index += sizeof(header);
+            packet.index += *flag_data_offset(&flags) * 4;
 
             if (socket.listen) {
                 auto copy    = packet;
@@ -364,7 +370,7 @@ std::expected<network::ethernet::packet> network::tcp::user_prepare_packet(char*
     auto& interface = network::select_interface(target_ip);
 
     // Ask the IP layer to craft a packet
-    network::ip::packet_descriptor desc{sizeof(header) + descriptor->payload_size, target_ip, 0x06};
+    network::ip::packet_descriptor desc{descriptor->payload_size + default_tcp_header_length, target_ip, 0x06};
     auto packet = network::ip::user_prepare_packet(buffer, interface, &desc);
 
     if (packet) {
@@ -388,7 +394,11 @@ std::expected<network::ethernet::packet> network::tcp::user_prepare_packet(char*
 }
 
 std::expected<void> network::tcp::finalize_packet(network::interface_descriptor& interface, network::socket& socket, network::ethernet::packet& p) {
-    p.index -= sizeof(header);
+    auto* tcp_header = reinterpret_cast<network::tcp::header*>(p.payload + p.tag(2));
+
+    auto flags = switch_endian_16(tcp_header->flags);
+
+    p.index -= *flag_data_offset(&flags) * 4;
 
     // Compute the checksum
     compute_checksum(p);