diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3042523..eb07c9b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,8 +14,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Removed
 
-- `RecvError` is no longer used. The read functions return `std::io::Error`
-  instead.
+- `RecvError` and `SendError` are no longer used. The recv/send functions return
+  `std::io::Error` instead.
 - Bump dependencies.
   - Update quinn to version 0.11.
   - Update rustls to version 0.23.
diff --git a/Cargo.toml b/Cargo.toml
index b9a1567..fef2a2d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,7 +16,6 @@ num_enum = "0.7"
 quinn = "0.11"
 quinn-proto = "0.11"
 serde = { version = "1", features = ["derive"] }
-thiserror = "1"
 tokio = "1"
 
 [dev-dependencies]
diff --git a/src/frame.rs b/src/frame.rs
index 63feb2e..d243f2c 100644
--- a/src/frame.rs
+++ b/src/frame.rs
@@ -4,7 +4,6 @@ use bincode::Options;
 use quinn::{RecvStream, SendStream};
 use serde::{Deserialize, Serialize};
 use std::{io, mem};
-use thiserror::Error;
 
 /// Receives and deserializes a message with a big-endian 4-byte length header.
 ///
@@ -132,32 +131,24 @@ fn from_transport_error_to_io_error(e: quinn_proto::TransportError) -> io::Error
     }
 }
 
-/// The error type for sending a message as a frame.
-#[derive(Debug, Error)]
-pub enum SendError {
-    #[error("message is too large")]
-    MessageTooLarge,
-    #[error("failed to write to a stream")]
-    WriteError(#[from] quinn::WriteError),
-}
-
 /// Sends a message as a stream of bytes with a big-endian 4-byte length header.
 ///
 /// `buf` will be cleared after the message is sent.
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge`: if the message is too large
-/// * `SendError::WriteError`: if the message could not be written
-pub async fn send<T>(send: &mut SendStream, buf: &mut Vec<u8>, msg: T) -> Result<(), SendError>
+/// Returns [`std::io::ErrorKind::InvalidData`] if the message is too large, or
+/// other errors if the message could not be written to the stream.
+pub async fn send<T>(send: &mut SendStream, buf: &mut Vec<u8>, msg: T) -> io::Result<()>
 where
     T: Serialize,
 {
     buf.resize(mem::size_of::<u32>(), 0);
     bincode::DefaultOptions::new()
         .serialize_into(&mut *buf, &msg)
-        .map_err(|_| SendError::MessageTooLarge)?;
-    let len = u32::try_from(buf.len() - 4).map_err(|_| SendError::MessageTooLarge)?;
+        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+    let len =
+        u32::try_from(buf.len() - 4).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
     buf[..mem::size_of::<u32>()].clone_from_slice(&len.to_be_bytes());
     send.write_all(buf).await?;
     buf.clear();
@@ -168,10 +159,10 @@ where
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge`: if the message is too large
-/// * `SendError::WriteError`: if the message could not be written
-pub async fn send_raw(send: &mut SendStream, buf: &[u8]) -> Result<(), SendError> {
-    let len = u32::try_from(buf.len()).map_err(|_| SendError::MessageTooLarge)?;
+/// Returns an error if the message is too large or could not be written.
+pub async fn send_raw(send: &mut SendStream, buf: &[u8]) -> io::Result<()> {
+    let len =
+        u32::try_from(buf.len()).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
     send.write_all(&len.to_be_bytes()).await?;
     send.write_all(buf).await?;
     Ok(())
diff --git a/src/message.rs b/src/message.rs
index 41f5200..b7c090a 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -1,6 +1,6 @@
 //! Functions and errors for handling messages.
 
-use crate::frame::{self, SendError};
+use crate::frame;
 use bincode::Options;
 use quinn::{RecvStream, SendStream};
 use serde::Serialize;
@@ -39,14 +39,14 @@ pub async fn recv_request_raw<'b>(
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge` if the message is too long to be serialized
-/// * `SendError::WriteError` if the message could not be written
+/// Returns [`std::io::ErrorKind::InvalidData`] if the message is too large, or
+/// other errors if the message could not be written to the stream.
 pub async fn send_request<C, B>(
     send: &mut SendStream,
     buf: &mut Vec<u8>,
     code: C,
     body: B,
-) -> Result<(), SendError>
+) -> io::Result<()>
 where
     C: Into<u32>,
     B: Serialize,
@@ -57,7 +57,7 @@ where
     buf.extend_from_slice(&code.into().to_le_bytes());
     bincode::DefaultOptions::new()
         .serialize_into(buf as &mut dyn Write, &body)
-        .map_err(|_| SendError::MessageTooLarge)?;
+        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
     frame::send_raw(send, buf).await?;
     buf.clear();
     Ok(())
@@ -69,15 +69,14 @@ where
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge` if `body` is too large to be serialized
-/// * `SendError::WriteError` if the message could not be written
+/// Returns [`std::io::ErrorKind::InvalidData`] if the message is too large, or
+/// other errors if the message could not be written to the stream.
 pub async fn send_ok<T: Serialize>(
     send: &mut SendStream,
     buf: &mut Vec<u8>,
     body: T,
-) -> Result<(), SendError> {
-    frame::send(send, buf, Ok(body) as Result<T, &str>).await?;
-    Ok(())
+) -> io::Result<()> {
+    frame::send(send, buf, Ok(body) as Result<T, &str>).await
 }
 
 /// Sends an `Err` response.
@@ -86,15 +85,14 @@ pub async fn send_ok<T: Serialize>(
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge` if `e` is too large to be serialized
-/// * `SendError::WriteError` if the message could not be written
+/// Returns [`std::io::ErrorKind::InvalidData`] if the message is too large, or
+/// other errors if the message could not be written to the stream.
 pub async fn send_err<E: fmt::Display>(
     send: &mut SendStream,
     buf: &mut Vec<u8>,
     e: E,
-) -> Result<(), SendError> {
-    frame::send(send, buf, Err(format!("{e:#}")) as Result<(), String>).await?;
-    Ok(())
+) -> io::Result<()> {
+    frame::send(send, buf, Err(format!("{e:#}")) as Result<(), String>).await
 }
 
 #[cfg(test)]
diff --git a/src/request.rs b/src/request.rs
index b20fc08..24ad878 100644
--- a/src/request.rs
+++ b/src/request.rs
@@ -27,16 +27,20 @@ pub fn parse_args<'de, T: Deserialize<'de>>(args: &'de [u8]) -> io::Result<T> {
 ///
 /// # Errors
 ///
-/// * `SendError::MessageTooLarge` if `e` is too large to be serialized
-/// * `SendError::WriteError` if the message could not be written
+/// Returns [`std::io::ErrorKind::InvalidData`] if the message is too large, or
+/// other errors if the message could not be written to the stream.
 pub async fn send_response<T: Serialize>(
     send: &mut SendStream,
     buf: &mut Vec<u8>,
     body: T,
-) -> Result<(), frame::SendError> {
-    match frame::send(send, buf, body).await {
-        Ok(()) => Ok(()),
-        Err(frame::SendError::WriteError(e)) => Err(frame::SendError::WriteError(e)),
-        Err(e) => message::send_err(send, buf, e).await,
+) -> io::Result<()> {
+    if let Err(e) = frame::send(send, buf, body).await {
+        if e.kind() == io::ErrorKind::InvalidData {
+            message::send_err(send, buf, e).await
+        } else {
+            Err(e)
+        }
+    } else {
+        Ok(())
     }
 }