diff --git a/serverconn.go b/serverconn.go
index 1c04e6ad..712febf8 100644
--- a/serverconn.go
+++ b/serverconn.go
@@ -34,7 +34,8 @@ type ServerConn struct {
 	nconn              net.Conn
 	br                 *bufio.Reader
 	bw                 *bufio.Writer
-	mutex              sync.Mutex
+	writeMutex         sync.Mutex
+	nextFramesEnabled  bool
 	framesEnabled      bool
 	readTimeoutEnabled bool
 }
@@ -51,7 +52,7 @@ func (sc *ServerConn) NetConn() net.Conn {
 
 // EnableFrames allows reading and writing TCP frames.
 func (sc *ServerConn) EnableFrames(v bool) {
-	sc.framesEnabled = v
+	sc.nextFramesEnabled = v
 }
 
 // EnableReadTimeout sets or removes the timeout on incoming packets.
@@ -247,17 +248,16 @@ func (sc *ServerConn) backgroundRead(handlers ServerConnReadHandlers, done chan
 	}
 
 	handleRequestOuter := func(req *base.Request) error {
-		sc.mutex.Lock()
-		defer sc.mutex.Unlock()
-
 		// check cseq
 		cseq, ok := req.Header["CSeq"]
 		if !ok || len(cseq) != 1 {
+			sc.writeMutex.Lock()
 			sc.nconn.SetWriteDeadline(time.Now().Add(sc.s.conf.WriteTimeout))
 			base.Response{
 				StatusCode: base.StatusBadRequest,
 				Header:     base.Header{},
 			}.Write(sc.bw)
+			sc.writeMutex.Unlock()
 			return ErrServerMissingCseq
 		}
 
@@ -277,9 +277,19 @@ func (sc *ServerConn) backgroundRead(handlers ServerConnReadHandlers, done chan
 			handlers.OnResponse(res)
 		}
 
+		sc.writeMutex.Lock()
+
 		sc.nconn.SetWriteDeadline(time.Now().Add(sc.s.conf.WriteTimeout))
 		res.Write(sc.bw)
 
+		// set framesEnabled after sending the response
+		// in order to start sending frames after the response
+		if sc.framesEnabled != sc.nextFramesEnabled {
+			sc.framesEnabled = sc.nextFramesEnabled
+		}
+
+		sc.writeMutex.Unlock()
+
 		return err
 	}
 
@@ -347,8 +357,8 @@ func (sc *ServerConn) Read(handlers ServerConnReadHandlers) chan error {
 
 // WriteFrame writes a frame.
 func (sc *ServerConn) WriteFrame(trackID int, streamType StreamType, content []byte) error {
-	sc.mutex.Lock()
-	defer sc.mutex.Unlock()
+	sc.writeMutex.Lock()
+	defer sc.writeMutex.Unlock()
 
 	if !sc.framesEnabled {
 		return ErrServerFramesDisabled