diff --git a/src/error.rs b/src/error.rs
index e224da7..a9c4ceb 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -3,7 +3,7 @@
 use std::{io, result, str, string};
 
 use crate::protocol::{frame::coding::Data, Message};
-use http::Response;
+use http::{header::HeaderName, Response};
 use thiserror::Error;
 
 /// Result type of all Tungstenite library calls.
@@ -138,7 +138,7 @@ pub enum CapacityError {
 }
 
 /// Indicates the specific type/cause of a protocol error.
-#[derive(Error, Debug, PartialEq, Eq, Clone, Copy)]
+#[derive(Error, Debug, PartialEq, Eq, Clone)]
 pub enum ProtocolError {
     /// Use of the wrong HTTP method (the WebSocket protocol requires the GET method be used).
     #[error("Unsupported HTTP method used - only GET is allowed")]
@@ -167,6 +167,10 @@ pub enum ProtocolError {
     /// Custom responses must be unsuccessful.
     #[error("Custom response must not be successful")]
     CustomResponseSuccessful,
+    /// Invalid header is passed. This header is formed by the library automatically
+    /// and must not be overwritten by the user.
+    #[error("Not allowed to pass overwrite the standard header {0}")]
+    InvalidHeader(HeaderName),
     /// No more data while still performing handshake.
     #[error("Handshake not finished")]
     HandshakeIncomplete,
diff --git a/src/handshake/client.rs b/src/handshake/client.rs
index 07c41c1..36d6262 100644
--- a/src/handshake/client.rs
+++ b/src/handshake/client.rs
@@ -5,7 +5,7 @@ use std::{
     marker::PhantomData,
 };
 
-use http::{HeaderMap, Request as HttpRequest, Response as HttpResponse, StatusCode};
+use http::{header, HeaderMap, Request as HttpRequest, Response as HttpResponse, StatusCode};
 use httparse::Status;
 use log::*;
 
@@ -125,6 +125,14 @@ fn generate_request(request: Request, key: &str) -> Result<Vec<u8>> {
     .unwrap();
 
     for (k, v) in request.headers() {
+        if k == header::CONNECTION
+            || k == header::UPGRADE
+            || k == header::SEC_WEBSOCKET_VERSION
+            || k == header::SEC_WEBSOCKET_KEY
+            || k == header::HOST
+        {
+            return Err(Error::Protocol(ProtocolError::InvalidHeader(k.clone())));
+        }
         let mut k = k.as_str();
         if k == "sec-websocket-protocol" {
             k = "Sec-WebSocket-Protocol";