diff --git a/nbhttp/websocket/dialer.go b/nbhttp/websocket/dialer.go
index 48506d01..abcf5b2f 100644
--- a/nbhttp/websocket/dialer.go
+++ b/nbhttp/websocket/dialer.go
@@ -245,7 +245,7 @@ func (d *Dialer) DialContext(ctx context.Context, urlStr string, requestHeader h
 		wsConn.OnClose(upgrader.onClose)
 
 		state.conn = wsConn
-		upgrader.Engine = parser.Engine
+		state.Engine = parser.Engine
 
 		if upgrader.openHandler != nil {
 			upgrader.openHandler(wsConn)
diff --git a/nbhttp/websocket/upgrader.go b/nbhttp/websocket/upgrader.go
index 429ce25c..666eb46d 100644
--- a/nbhttp/websocket/upgrader.go
+++ b/nbhttp/websocket/upgrader.go
@@ -49,8 +49,6 @@ type Upgrader struct {
 	messageHandler   func(c *Conn, messageType MessageType, data []byte)
 	dataFrameHandler func(c *Conn, messageType MessageType, fin bool, data []byte)
 	onClose          func(c *Conn, err error)
-
-	Engine *nbhttp.Engine
 }
 type connState struct {
 	common             *Upgrader
@@ -60,6 +58,7 @@ type connState struct {
 	opcode             MessageType
 	buffer             []byte
 	message            []byte
+	Engine             *nbhttp.Engine
 }
 
 // CompressionEnabled .
@@ -282,7 +281,7 @@ func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeade
 	}
 
 	state.conn = newConn(u, conn, subprotocol, compress)
-	u.Engine = parser.Engine
+	state.Engine = parser.Engine
 	state.conn.Engine = parser.Engine
 
 	if u.openHandler != nil {
@@ -364,10 +363,10 @@ func (u *connState) Read(p *nbhttp.Parser, data []byte) error {
 						err = ErrMessageTooLarge
 						break
 					}
-					frame = u.common.Engine.BodyAllocator.Malloc(bl)
+					frame = u.Engine.BodyAllocator.Malloc(bl)
 					copy(frame, body)
 				}
-				if u.opcode == TextMessage && len(frame) > 0 && !u.common.Engine.CheckUtf8(frame) {
+				if u.opcode == TextMessage && len(frame) > 0 && !u.Engine.CheckUtf8(frame) {
 					u.conn.Close()
 				} else {
 					u.common.handleDataFrame(p, u.conn, u.opcode, fin, frame)
@@ -375,7 +374,7 @@ func (u *connState) Read(p *nbhttp.Parser, data []byte) error {
 			}
 			if bl > 0 && u.common.messageHandler != nil {
 				if u.message == nil {
-					u.message = u.common.Engine.BodyAllocator.Malloc(len(body))
+					u.message = u.Engine.BodyAllocator.Malloc(len(body))
 					if u.isMessageTooLarge(len(body)) {
 						err = ErrMessageTooLarge
 						break
@@ -395,7 +394,7 @@ func (u *connState) Read(p *nbhttp.Parser, data []byte) error {
 						var b []byte
 						rc := decompressReader(io.MultiReader(bytes.NewBuffer(u.message), strings.NewReader(flateReaderTail)))
 						b, err = u.readAll(rc, len(u.message)*2)
-						u.common.Engine.BodyAllocator.Free(u.message)
+						u.Engine.BodyAllocator.Free(u.message)
 						u.message = b
 						rc.Close()
 						if err != nil {
@@ -418,7 +417,7 @@ func (u *connState) Read(p *nbhttp.Parser, data []byte) error {
 					err = ErrMessageTooLarge
 					break
 				}
-				frame = u.common.Engine.BodyAllocator.Malloc(len(body))
+				frame = u.Engine.BodyAllocator.Malloc(len(body))
 				copy(frame, body)
 			}
 			u.handleProtocolMessage(p, opcode, frame)
@@ -468,7 +467,7 @@ func (u *Upgrader) handleDataFrame(p *nbhttp.Parser, c *Conn, opcode MessageType
 }
 
 func (u *connState) handleMessage(p *nbhttp.Parser, opcode MessageType, body []byte) {
-	if u.opcode == TextMessage && !u.common.Engine.CheckUtf8(u.message) {
+	if u.opcode == TextMessage && !u.Engine.CheckUtf8(u.message) {
 		u.conn.Close()
 		return
 	}
@@ -482,8 +481,8 @@ func (u *connState) handleMessage(p *nbhttp.Parser, opcode MessageType, body []b
 func (u *connState) handleProtocolMessage(p *nbhttp.Parser, opcode MessageType, body []byte) {
 	p.Execute(func() {
 		u.common.handleWsMessage(u.conn, opcode, body)
-		if len(body) > 0 && u.common.Engine.ReleaseWebsocketPayload {
-			u.common.Engine.BodyAllocator.Free(body)
+		if len(body) > 0 && u.Engine.ReleaseWebsocketPayload {
+			u.Engine.BodyAllocator.Free(body)
 		}
 	})
 }
@@ -871,7 +870,7 @@ func nextTokenOrQuoted(s string) (value string, rest string) {
 
 func (u *connState) readAll(r io.Reader, size int) ([]byte, error) {
 	const maxAppendSize = 1024 * 1024 * 4
-	buf := u.common.Engine.BodyAllocator.Malloc(size)[0:0]
+	buf := u.Engine.BodyAllocator.Malloc(size)[0:0]
 	for {
 		n, err := r.Read(buf[len(buf):cap(buf)])
 		if n > 0 {