diff --git a/examples/callback-error.rs b/examples/callback-error.rs
index ee51136..cf78a2e 100644
--- a/examples/callback-error.rs
+++ b/examples/callback-error.rs
@@ -13,7 +13,7 @@ fn main() {
             let callback = |_req: &Request, _resp| {
                 let resp = Response::builder()
                     .status(StatusCode::FORBIDDEN)
-                    .body("Access denied".into())
+                    .body(Some("Access denied".into()))
                     .unwrap();
                 Err(resp)
             };
diff --git a/src/error.rs b/src/error.rs
index 9d6576e..c830024 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -65,7 +65,7 @@ pub enum Error {
     /// HTTP error.
     #[error("HTTP error: {}", .0.status())]
     #[cfg(feature = "handshake")]
-    Http(Response<Vec<u8>>),
+    Http(Response<Option<Vec<u8>>>),
     /// HTTP format error.
     #[error("HTTP format error: {0}")]
     #[cfg(feature = "handshake")]
diff --git a/src/handshake/client.rs b/src/handshake/client.rs
index 87305f4..aaeabb7 100644
--- a/src/handshake/client.rs
+++ b/src/handshake/client.rs
@@ -26,7 +26,7 @@ use crate::{
 pub type Request = HttpRequest<()>;
 
 /// Client response type.
-pub type Response = HttpResponse<Vec<u8>>;
+pub type Response = HttpResponse<Option<Vec<u8>>>;
 
 /// Client handshake role.
 #[derive(Debug)]
@@ -86,7 +86,7 @@ impl<S: Read + Write> HandshakeRole for ClientHandshake<S> {
                 let result = match self.verify_data.verify_response(result) {
                     Ok(r) => r,
                     Err(Error::Http(mut e)) => {
-                        *e.body_mut() = tail;
+                        *e.body_mut() = Some(tail);
                         return Err(Error::Http(e))
                     },
                     Err(e) => return Err(e),
@@ -263,7 +263,7 @@ impl<'h, 'b: 'h> FromHttparse<httparse::Response<'h, 'b>> for Response {
 
         let headers = HeaderMap::from_httparse(raw.headers)?;
 
-        let mut response = Response::new(vec![]);
+        let mut response = Response::new(None);
         *response.status_mut() = StatusCode::from_u16(raw.code.expect("Bug: no HTTP status code"))?;
         *response.headers_mut() = headers;
         // TODO: httparse only supports HTTP 0.9/1.0/1.1 but not HTTP 2.0
diff --git a/src/handshake/server.rs b/src/handshake/server.rs
index 7e3a57f..4cf1c5c 100644
--- a/src/handshake/server.rs
+++ b/src/handshake/server.rs
@@ -30,7 +30,7 @@ pub type Request = HttpRequest<()>;
 pub type Response = HttpResponse<()>;
 
 /// Server error response type.
-pub type ErrorResponse = HttpResponse<Vec<u8>>;
+pub type ErrorResponse = HttpResponse<Option<String>>;
 
 fn create_parts<T>(request: &HttpRequest<T>) -> Result<Builder> {
     if request.method() != http::Method::GET {
@@ -265,7 +265,9 @@ impl<S: Read + Write, C: Callback> HandshakeRole for ServerHandshake<S, C> {
                         let mut output = vec![];
                         write_response(&mut output, resp)?;
 
-                        output.extend_from_slice(resp.body());
+                        if let Some(body) = resp.body() {
+                            output.extend_from_slice(body.as_bytes());
+                        }
 
                         ProcessingResult::Continue(HandshakeMachine::start_write(stream, output))
                     }
@@ -275,7 +277,10 @@ impl<S: Read + Write, C: Callback> HandshakeRole for ServerHandshake<S, C> {
             StageResult::DoneWriting(stream) => {
                 if let Some(err) = self.error_response.take() {
                     debug!("Server handshake failed.");
-                    return Err(Error::Http(err));
+
+                    let (parts, body) = err.into_parts();
+                    let body = body.map(|b| b.as_bytes().to_vec());
+                    return Err(Error::Http(http::Response::from_parts(parts, body)));
                 } else {
                     debug!("Server handshake done.");
                     let websocket = WebSocket::from_raw_socket(stream, Role::Server, self.config);