diff --git a/nbhttp/websocket/conn.go b/nbhttp/websocket/conn.go
index 8c3f50da..ce5e3ccd 100644
--- a/nbhttp/websocket/conn.go
+++ b/nbhttp/websocket/conn.go
@@ -608,6 +608,21 @@ func (c *Conn) WriteMessage(messageType MessageType, data []byte) error {
 	return c.writeFrame(messageType, true, true, []byte{}, compress)
 }
 
+// Keepalive .
+func (c *Conn) Keepalive(d time.Duration) *time.Timer {
+	var fn func()
+	var timer *time.Timer
+	fn = func() {
+		err := c.WriteMessage(PingMessage, []byte{})
+		if err != nil {
+			return
+		}
+		timer.Reset(d)
+	}
+	timer = time.AfterFunc(d, fn)
+	return timer
+}
+
 // Session returns user session.
 func (c *Conn) Session() interface{} {
 	if c.chSessionInited == nil {
diff --git a/protocol_stack.go b/protocol_stack.go
index f0267858..cb6a2c36 100644
--- a/protocol_stack.go
+++ b/protocol_stack.go
@@ -18,11 +18,18 @@ func (ps *ProtocolStack) Add(p Protocol) {
 }
 
 func (ps *ProtocolStack) Delete(p Protocol) {
-	for i, v := range ps.stack {
-		if v == p {
+	i := len(ps.stack) - 1
+	for i >= 0 {
+		if ps.stack[i] == p {
 			ps.stack[i] = nil
+			if i+1 > len(ps.stack)-1 {
+				ps.stack = ps.stack[:i]
+			} else {
+				ps.stack = append(ps.stack[:i], ps.stack[i+1:]...)
+			}
 			return
 		}
+		i--
 	}
 }