diff --git a/client.go b/client.go
index 8e90de2..41f8ed5 100644
--- a/client.go
+++ b/client.go
@@ -201,7 +201,7 @@ func (d *Dialer) Dial(urlStr string, requestHeader http.Header) (*Conn, *http.Re
 	}
 
 	if d.EnableCompression {
-		req.Header.Set("Sec-Websocket-Extensions", "permessage-deflate; server_no_context_takeover; client_no_context_takeover")
+		req.Header["Sec-WebSocket-Extensions"] = []string{"permessage-deflate; server_no_context_takeover; client_no_context_takeover"}
 	}
 
 	var deadline time.Time
diff --git a/server.go b/server.go
index 3e96a00..aee2705 100644
--- a/server.go
+++ b/server.go
@@ -103,7 +103,7 @@ func (u *Upgrader) selectSubprotocol(r *http.Request, responseHeader http.Header
 //
 // The responseHeader is included in the response to the client's upgrade
 // request. Use the responseHeader to specify cookies (Set-Cookie) and the
-// application negotiated subprotocol (Sec-Websocket-Protocol).
+// application negotiated subprotocol (Sec-WebSocket-Protocol).
 //
 // If the upgrade fails, then Upgrade replies to the client with an HTTP error
 // response.
@@ -127,7 +127,7 @@ func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeade
 	}
 
 	if _, ok := responseHeader["Sec-Websocket-Extensions"]; ok {
-		return u.returnError(w, r, http.StatusInternalServerError, "websocket: application specific 'Sec-Websocket-Extensions' headers are unsupported")
+		return u.returnError(w, r, http.StatusInternalServerError, "websocket: application specific 'Sec-WebSocket-Extensions' headers are unsupported")
 	}
 
 	checkOrigin := u.CheckOrigin
@@ -140,7 +140,7 @@ func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeade
 
 	challengeKey := r.Header.Get("Sec-Websocket-Key")
 	if challengeKey == "" {
-		return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: `Sec-Websocket-Key' header is missing or blank")
+		return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: `Sec-WebSocket-Key' header is missing or blank")
 	}
 
 	subprotocol := u.selectSubprotocol(r, responseHeader)
@@ -190,12 +190,12 @@ func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeade
 	p = append(p, computeAcceptKey(challengeKey)...)
 	p = append(p, "\r\n"...)
 	if c.subprotocol != "" {
-		p = append(p, "Sec-Websocket-Protocol: "...)
+		p = append(p, "Sec-WebSocket-Protocol: "...)
 		p = append(p, c.subprotocol...)
 		p = append(p, "\r\n"...)
 	}
 	if compress {
-		p = append(p, "Sec-Websocket-Extensions: permessage-deflate; server_no_context_takeover; client_no_context_takeover\r\n"...)
+		p = append(p, "Sec-WebSocket-Extensions: permessage-deflate; server_no_context_takeover; client_no_context_takeover\r\n"...)
 	}
 	for k, vs := range responseHeader {
 		if k == "Sec-Websocket-Protocol" {