diff --git a/src/stream/tcp.rs b/src/stream/tcp.rs
index 4ece70d..6bf154a 100644
--- a/src/stream/tcp.rs
+++ b/src/stream/tcp.rs
@@ -9,7 +9,7 @@ use crate::{
     },
     stream::tcb::{PacketType, Tcb, TcpState},
 };
-use etherparse::{IpNumber, Ipv4Header, Ipv6FlowLabel, TcpHeader, TcpOptionElement};
+use etherparse::{IpNumber, Ipv4Header, Ipv6FlowLabel, TcpHeader};
 use std::{
     future::Future,
     io::ErrorKind::{BrokenPipe, ConnectionRefused, InvalidInput, UnexpectedEof},
@@ -28,6 +28,7 @@ const CLOSE_WAIT_TIMEOUT: Duration = Duration::from_secs(5);
 const LAST_ACK_MAX_RETRIES: usize = 3;
 const LAST_ACK_TIMEOUT: Duration = Duration::from_millis(500);
 const TIMEOUT: Duration = Duration::from_secs(60);
+const TCP_HEADER_LEN: u16 = 20;
 
 #[non_exhaustive]
 #[derive(Debug, Clone)]
@@ -451,7 +452,16 @@ async fn tcp_main_logic_loop(
             &up_packet_sender,
             network_tuple,
             &tcb,
-            config.options.as_ref(),
+            config.options.as_ref().map(|o| {
+                (
+                    o,
+                    if network_tuple.src.is_ipv4() && network_tuple.dst.is_ipv4() {
+                        tcb.get_mtu() - 20 - TCP_HEADER_LEN
+                    } else {
+                        tcb.get_mtu() - 40 - TCP_HEADER_LEN
+                    },
+                )
+            }),
             ACK | SYN,
             None,
             None,
@@ -861,7 +871,7 @@ pub(crate) fn write_packet_to_device(
     up_packet_sender: &PacketSender,
     tuple: NetworkTuple,
     tcb: &Tcb,
-    options: Option<&Vec<TcpOptions>>,
+    options: Option<(&Vec<TcpOptions>, u16)>,
     flags: u8,
     seq: Option<SeqNum>,
     payload: Option<Vec<u8>>,
@@ -899,7 +909,7 @@ pub(crate) fn create_raw_packet(
     ack: u32,
     win: u16,
     mut payload: Vec<u8>,
-    options: Option<&Vec<TcpOptions>>,
+    options: Option<(&Vec<TcpOptions>, u16)>,
 ) -> std::io::Result<NetworkPacket> {
     let mut tcp_header = etherparse::TcpHeader::new(src_addr.port(), dst_addr.port(), seq, win);
     tcp_header.acknowledgment_number = ack;
@@ -909,17 +919,19 @@ pub(crate) fn create_raw_packet(
     tcp_header.fin = flags & FIN != 0;
     tcp_header.psh = flags & PSH != 0;
 
-    if let Some(opts) = options {
+    if let Some((opts, mut mss)) = options {
         let mut tcp_options = Vec::new();
         for opt in opts {
             match opt {
-                TcpOptions::MaximumSegmentSize(mss) => tcp_options.push(TcpOptionElement::MaximumSegmentSize(*mss)),
+                TcpOptions::MaximumSegmentSize(fixed_mss) => mss = *fixed_mss,
             }
         }
+        tcp_options.push(etherparse::TcpOptionElement::MaximumSegmentSize(mss));
         tcp_header
             .set_options(&tcp_options)
             .map_err(|e| std::io::Error::new(InvalidInput, e))?;
     }
+
     let ip_header = match (src_addr.ip(), dst_addr.ip()) {
         (std::net::IpAddr::V4(src), std::net::IpAddr::V4(dst)) => {
             let mut ip_h =