diff --git a/quinn-proto/src/connection/datagrams.rs b/quinn-proto/src/connection/datagrams.rs
index abadbe9166..a9dadaf7d2 100644
--- a/quinn-proto/src/connection/datagrams.rs
+++ b/quinn-proto/src/connection/datagrams.rs
@@ -1,6 +1,6 @@
 use std::collections::VecDeque;
 
-use bytes::{Bytes, BytesMut};
+use bytes::Bytes;
 use thiserror::Error;
 use tracing::{debug, trace};
 
@@ -127,7 +127,7 @@ impl DatagramState {
         Ok(was_empty)
     }
 
-    pub(super) fn write(&mut self, buf: &mut BytesMut, max_size: usize) -> bool {
+    pub(super) fn write(&mut self, buf: &mut Vec<u8>, max_size: usize) -> bool {
         let datagram = match self.outgoing.pop_front() {
             Some(x) => x,
             None => return false,
diff --git a/quinn-proto/src/connection/mod.rs b/quinn-proto/src/connection/mod.rs
index d3cc8b25fd..c7af6eebbd 100644
--- a/quinn-proto/src/connection/mod.rs
+++ b/quinn-proto/src/connection/mod.rs
@@ -459,7 +459,7 @@ impl Connection {
         &mut self,
         now: Instant,
         max_datagrams: usize,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
     ) -> Option<Transmit> {
         assert!(max_datagrams != 0);
         let max_datagrams = match self.config.enable_segmentation_offload {
@@ -2920,7 +2920,7 @@ impl Connection {
         &mut self,
         now: Instant,
         space_id: SpaceId,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
         max_size: usize,
         pn: u64,
     ) -> SentFrames {
@@ -3139,7 +3139,7 @@ impl Connection {
         receiving_ecn: bool,
         sent: &mut SentFrames,
         space: &mut PacketSpace,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
         stats: &mut ConnectionStats,
     ) {
         debug_assert!(!space.pending_acks.ranges().is_empty());
diff --git a/quinn-proto/src/connection/packet_builder.rs b/quinn-proto/src/connection/packet_builder.rs
index c53d09a2db..8e362b0157 100644
--- a/quinn-proto/src/connection/packet_builder.rs
+++ b/quinn-proto/src/connection/packet_builder.rs
@@ -1,6 +1,6 @@
 use std::time::Instant;
 
-use bytes::{Bytes, BytesMut};
+use bytes::Bytes;
 use rand::Rng;
 use tracing::{trace, trace_span};
 
@@ -32,7 +32,7 @@ impl PacketBuilder {
     pub(super) fn new(
         now: Instant,
         space_id: SpaceId,
-        buffer: &mut BytesMut,
+        buffer: &mut Vec<u8>,
         buffer_capacity: usize,
         datagram_start: usize,
         ack_eliciting: bool,
@@ -174,7 +174,7 @@ impl PacketBuilder {
         now: Instant,
         conn: &mut Connection,
         sent: Option<SentFrames>,
-        buffer: &mut BytesMut,
+        buffer: &mut Vec<u8>,
     ) {
         let ack_eliciting = self.ack_eliciting;
         let exact_number = self.exact_number;
@@ -217,7 +217,7 @@ impl PacketBuilder {
     }
 
     /// Encrypt packet, returning the length of the packet and whether padding was added
-    pub(super) fn finish(self, conn: &mut Connection, buffer: &mut BytesMut) -> (usize, bool) {
+    pub(super) fn finish(self, conn: &mut Connection, buffer: &mut Vec<u8>) -> (usize, bool) {
         let pad = buffer.len() < self.min_size;
         if pad {
             trace!("PADDING * {}", self.min_size - buffer.len());
diff --git a/quinn-proto/src/connection/streams/state.rs b/quinn-proto/src/connection/streams/state.rs
index 9413da75b1..23bb6e8099 100644
--- a/quinn-proto/src/connection/streams/state.rs
+++ b/quinn-proto/src/connection/streams/state.rs
@@ -4,7 +4,7 @@ use std::{
     mem,
 };
 
-use bytes::{BufMut, BytesMut};
+use bytes::BufMut;
 use rustc_hash::FxHashMap;
 use tracing::{debug, trace};
 
@@ -365,7 +365,7 @@ impl StreamsState {
 
     pub(in crate::connection) fn write_control_frames(
         &mut self,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
         pending: &mut Retransmits,
         retransmits: &mut ThinRetransmits,
         stats: &mut FrameStats,
@@ -491,7 +491,7 @@ impl StreamsState {
 
     pub(crate) fn write_stream_frames(
         &mut self,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
         max_buf_size: usize,
     ) -> StreamMetaVec {
         let mut stream_frames = StreamMetaVec::new();
@@ -925,7 +925,7 @@ mod tests {
         connection::State as ConnState, connection::Streams, ReadableError, RecvStream, SendStream,
         TransportErrorCode, WriteError,
     };
-    use bytes::{Bytes, BytesMut};
+    use bytes::Bytes;
 
     fn make(side: Side) -> StreamsState {
         StreamsState::new(
@@ -1317,7 +1317,7 @@ mod tests {
         high.set_priority(1).unwrap();
         high.write(b"high").unwrap();
 
-        let mut buf = BytesMut::with_capacity(40);
+        let mut buf = Vec::with_capacity(40);
         let meta = server.write_stream_frames(&mut buf, 40);
         assert_eq!(meta[0].id, id_high);
         assert_eq!(meta[1].id, id_mid);
@@ -1376,7 +1376,7 @@ mod tests {
         };
         high.set_priority(-1).unwrap();
 
-        let mut buf = BytesMut::with_capacity(1000);
+        let mut buf = Vec::with_capacity(1000);
         let meta = server.write_stream_frames(&mut buf, 40);
         assert_eq!(meta.len(), 1);
         assert_eq!(meta[0].id, id_high);
diff --git a/quinn-proto/src/endpoint.rs b/quinn-proto/src/endpoint.rs
index 3d61881d15..05e4bf0680 100644
--- a/quinn-proto/src/endpoint.rs
+++ b/quinn-proto/src/endpoint.rs
@@ -127,7 +127,7 @@ impl Endpoint {
         local_ip: Option<IpAddr>,
         ecn: Option<EcnCodepoint>,
         data: BytesMut,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
     ) -> Option<DatagramEvent> {
         let datagram_len = data.len();
         let (first_decode, remaining) = match PartialDecode::new(
@@ -267,7 +267,7 @@ impl Endpoint {
         inciting_dgram_len: usize,
         addresses: FourTuple,
         dst_cid: &ConnectionId,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
     ) -> Option<Transmit> {
         /// Minimum amount of padding for the stateless reset to look like a short-header packet
         const MIN_PADDING_LEN: usize = 5;
@@ -404,7 +404,7 @@ impl Endpoint {
         mut packet: Packet,
         rest: Option<BytesMut>,
         crypto: &Keys,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
     ) -> Option<DatagramEvent> {
         let (src_cid, dst_cid, token, packet_number, version) = match packet.header {
             Header::Initial {
@@ -633,7 +633,7 @@ impl Endpoint {
         crypto: &Keys,
         remote_id: &ConnectionId,
         reason: TransportError,
-        buf: &mut BytesMut,
+        buf: &mut Vec<u8>,
     ) -> Transmit {
         // We don't need to worry about CID collisions in initial closes because the peer
         // shouldn't respond, and if it does, and the CID collides, we'll just drop the
diff --git a/quinn-proto/src/frame.rs b/quinn-proto/src/frame.rs
index fb953b0e77..e75781ae89 100644
--- a/quinn-proto/src/frame.rs
+++ b/quinn-proto/src/frame.rs
@@ -4,7 +4,7 @@ use std::{
     ops::{Range, RangeInclusive},
 };
 
-use bytes::{Buf, BufMut, Bytes, BytesMut};
+use bytes::{Buf, BufMut, Bytes};
 use tinyvec::TinyVec;
 
 use crate::{
@@ -888,7 +888,7 @@ impl FrameStruct for Datagram {
 }
 
 impl Datagram {
-    pub(crate) fn encode(&self, length: bool, out: &mut BytesMut) {
+    pub(crate) fn encode(&self, length: bool, out: &mut Vec<u8>) {
         out.write(Type(*DATAGRAM_TYS.start() | u64::from(length))); // 1 byte
         if length {
             // Safe to unwrap because we check length sanity before queueing datagrams
diff --git a/quinn-proto/src/packet.rs b/quinn-proto/src/packet.rs
index b70eb98f78..13f670a40f 100644
--- a/quinn-proto/src/packet.rs
+++ b/quinn-proto/src/packet.rs
@@ -271,7 +271,7 @@ pub(crate) enum Header {
 }
 
 impl Header {
-    pub(crate) fn encode(&self, w: &mut BytesMut) -> PartialEncode {
+    pub(crate) fn encode(&self, w: &mut Vec<u8>) -> PartialEncode {
         use self::Header::*;
         let start = w.len();
         match *self {
@@ -846,7 +846,7 @@ mod tests {
 
         let dcid = ConnectionId::new(&hex!("06b858ec6f80452b"));
         let client = initial_keys(Version::V1, &dcid, Side::Client);
-        let mut buf = BytesMut::new();
+        let mut buf = Vec::new();
         let header = Header::Initial {
             number: PacketNumber::U8(0),
             src_cid: ConnectionId::new(&[]),
@@ -877,7 +877,7 @@ mod tests {
 
         let server = initial_keys(Version::V1, &dcid, Side::Server);
         let supported_versions = DEFAULT_SUPPORTED_VERSIONS.to_vec();
-        let decode = PartialDecode::new(buf, 0, &supported_versions, false)
+        let decode = PartialDecode::new(buf.as_slice().into(), 0, &supported_versions, false)
             .unwrap()
             .0;
         let mut packet = decode.finish(Some(&*server.header.remote)).unwrap();
diff --git a/quinn-proto/src/tests/mod.rs b/quinn-proto/src/tests/mod.rs
index c41f3592d0..19e5dfe92f 100644
--- a/quinn-proto/src/tests/mod.rs
+++ b/quinn-proto/src/tests/mod.rs
@@ -7,7 +7,7 @@ use std::{
 };
 
 use assert_matches::assert_matches;
-use bytes::{Bytes, BytesMut};
+use bytes::Bytes;
 use hex_literal::hex;
 use rand::RngCore;
 use ring::hmac;
@@ -34,7 +34,7 @@ fn version_negotiate_server() {
         None,
     );
     let now = Instant::now();
-    let mut buf = BytesMut::with_capacity(server.config().get_max_udp_payload_size() as usize);
+    let mut buf = Vec::with_capacity(server.config().get_max_udp_payload_size() as usize);
     let event = server.handle(
         now,
         client_addr,
@@ -76,7 +76,7 @@ fn version_negotiate_client() {
         .connect(Instant::now(), client_config(), server_addr, "localhost")
         .unwrap();
     let now = Instant::now();
-    let mut buf = BytesMut::with_capacity(client.config().get_max_udp_payload_size() as usize);
+    let mut buf = Vec::with_capacity(client.config().get_max_udp_payload_size() as usize);
     let opt_event = client.handle(
         now,
         server_addr,
@@ -1941,7 +1941,7 @@ fn malformed_token_len() {
         true,
         None,
     );
-    let mut buf = BytesMut::with_capacity(server.config().get_max_udp_payload_size() as usize);
+    let mut buf = Vec::with_capacity(server.config().get_max_udp_payload_size() as usize);
     server.handle(
         Instant::now(),
         client_addr,
diff --git a/quinn-proto/src/tests/util.rs b/quinn-proto/src/tests/util.rs
index cd7bb11239..07ce9337af 100644
--- a/quinn-proto/src/tests/util.rs
+++ b/quinn-proto/src/tests/util.rs
@@ -331,7 +331,7 @@ impl TestEndpoint {
             }
         }
         let buffer_size = self.endpoint.config().get_max_udp_payload_size() as usize;
-        let mut buf = BytesMut::with_capacity(buffer_size);
+        let mut buf = Vec::with_capacity(buffer_size);
 
         while self.inbound.front().map_or(false, |x| x.0 <= now) {
             let (recv_time, ecn, packet) = self.inbound.pop_front().unwrap();
@@ -354,8 +354,11 @@ impl TestEndpoint {
                     }
                     DatagramEvent::Response(transmit) => {
                         let size = transmit.size;
-                        self.outbound
-                            .extend(split_transmit(transmit, buf.split_to(size).freeze()));
+                        self.outbound.extend(split_transmit(
+                            transmit,
+                            Bytes::copy_from_slice(&buf[..size]),
+                        ));
+                        buf.clear();
                     }
                 }
             }
@@ -380,8 +383,11 @@ impl TestEndpoint {
                 }
                 while let Some(transmit) = conn.poll_transmit(now, MAX_DATAGRAMS, &mut buf) {
                     let size = transmit.size;
-                    self.outbound
-                        .extend(split_transmit(transmit, buf.split_to(size).freeze()));
+                    self.outbound.extend(split_transmit(
+                        transmit,
+                        Bytes::copy_from_slice(&buf[..size]),
+                    ));
+                    buf.clear();
                 }
                 self.timeout = conn.poll_timeout();
             }
diff --git a/quinn/src/connection.rs b/quinn/src/connection.rs
index cb96f68428..9b5ac049ce 100644
--- a/quinn/src/connection.rs
+++ b/quinn/src/connection.rs
@@ -10,7 +10,7 @@ use std::{
     time::{Duration, Instant},
 };
 
-use bytes::{Bytes, BytesMut};
+use bytes::Bytes;
 use pin_project_lite::pin_project;
 use rustc_hash::FxHashMap;
 use thiserror::Error;
@@ -795,7 +795,7 @@ impl ConnectionRef {
                 io_poller: socket.clone().create_io_poller(),
                 socket,
                 runtime,
-                send_buffer: BytesMut::new(),
+                send_buffer: Vec::new(),
                 buffered_transmit: None,
             }),
             shared: Shared::default(),
@@ -876,7 +876,7 @@ pub(crate) struct State {
     socket: Arc<dyn AsyncUdpSocket>,
     io_poller: Pin<Box<dyn UdpPoller>>,
     runtime: Arc<dyn Runtime>,
-    send_buffer: BytesMut,
+    send_buffer: Vec<u8>,
     /// We buffer a transmit when the underlying I/O would block
     buffered_transmit: Option<proto::Transmit>,
 }
diff --git a/quinn/src/endpoint.rs b/quinn/src/endpoint.rs
index 46fd9f29ee..c6054f3de1 100644
--- a/quinn/src/endpoint.rs
+++ b/quinn/src/endpoint.rs
@@ -414,7 +414,7 @@ impl State {
                         let mut data: BytesMut = buf[0..meta.len].into();
                         while !data.is_empty() {
                             let buf = data.split_to(meta.stride.min(data.len()));
-                            let mut response_buffer = BytesMut::new();
+                            let mut response_buffer = Vec::new();
                             match self.inner.handle(
                                 now,
                                 meta.addr,