diff --git a/go.mod b/go.mod
index 1df8b24..cbdb6d0 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/urfave/cli v1.22.12
 	github.com/xtaci/kcp-go/v5 v5.6.2
-	github.com/xtaci/smux v1.5.19
+	github.com/xtaci/smux v1.5.20
 	github.com/xtaci/tcpraw v1.2.25
 	golang.org/x/crypto v0.5.0
 )
diff --git a/go.sum b/go.sum
index 49e9e59..e76b973 100644
--- a/go.sum
+++ b/go.sum
@@ -74,6 +74,8 @@ github.com/xtaci/smux v1.5.18 h1:NRH2dIxcO1w5dsNpQxSrxfhxjk4YNg6TrS/Nj0FuUPc=
 github.com/xtaci/smux v1.5.18/go.mod h1:OMlQbT5vcgl2gb49mFkYo6SMf+zP3rcjcwQz7ZU7IGY=
 github.com/xtaci/smux v1.5.19 h1:QFoVBZPuJnoTs8QQ52TO2469nz8KxGHDpiEb+s3QzCQ=
 github.com/xtaci/smux v1.5.19/go.mod h1:OMlQbT5vcgl2gb49mFkYo6SMf+zP3rcjcwQz7ZU7IGY=
+github.com/xtaci/smux v1.5.20 h1:7pw7PLSW1MfiiRVBB27T5cFLGws1GAJP9ZDP+V+40dw=
+github.com/xtaci/smux v1.5.20/go.mod h1:OMlQbT5vcgl2gb49mFkYo6SMf+zP3rcjcwQz7ZU7IGY=
 github.com/xtaci/tcpraw v1.2.25 h1:VDlqo0op17JeXBM6e2G9ocCNLOJcw9mZbobMbJjo0vk=
 github.com/xtaci/tcpraw v1.2.25/go.mod h1:dKyZ2V75s0cZ7cbgJYdxPvms7af0joIeOyx1GgJQbLk=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
diff --git a/vendor/github.com/xtaci/smux/session.go b/vendor/github.com/xtaci/smux/session.go
index 4659743..28fdd04 100644
--- a/vendor/github.com/xtaci/smux/session.go
+++ b/vendor/github.com/xtaci/smux/session.go
@@ -13,6 +13,7 @@ import (
 
 const (
 	defaultAcceptBacklog = 1024
+	maxShaperSize        = 1024
 )
 
 var (
@@ -420,8 +421,10 @@ func (s *Session) shaperLoop() {
 	var reqs shaperHeap
 	var next writeRequest
 	var chWrite chan writeRequest
+	var chShaper chan writeRequest
 
 	for {
+		// chWrite is not available until it has packet to send
 		if len(reqs) > 0 {
 			chWrite = s.writes
 			next = heap.Pop(&reqs).(writeRequest)
@@ -429,10 +432,22 @@ func (s *Session) shaperLoop() {
 			chWrite = nil
 		}
 
+		// control heap size, chShaper is not available until packets are less than maximum allowed
+		if len(reqs) >= maxShaperSize {
+			chShaper = nil
+		} else {
+			chShaper = s.shaper
+		}
+
+		// assertion on non nil
+		if chShaper == nil && chWrite == nil {
+			panic("both channel are nil")
+		}
+
 		select {
 		case <-s.die:
 			return
-		case r := <-s.shaper:
+		case r := <-chShaper:
 			if chWrite != nil { // next is valid, reshape
 				heap.Push(&reqs, next)
 			}
diff --git a/vendor/github.com/xtaci/smux/stream.go b/vendor/github.com/xtaci/smux/stream.go
index a95fb56..94e858e 100644
--- a/vendor/github.com/xtaci/smux/stream.go
+++ b/vendor/github.com/xtaci/smux/stream.go
@@ -325,7 +325,7 @@ func (s *Stream) Write(b []byte) (n int, err error) {
 		}
 		frame.data = bts[:sz]
 		bts = bts[sz:]
-		n, err := s.sess.writeFrameInternal(frame, deadline, s.numWritten)
+		n, err := s.sess.writeFrameInternal(frame, deadline, 0)
 		s.numWritten++
 		sent += n
 		if err != nil {
@@ -393,7 +393,7 @@ func (s *Stream) writeV2(b []byte) (n int, err error) {
 				}
 				frame.data = bts[:sz]
 				bts = bts[sz:]
-				n, err := s.sess.writeFrameInternal(frame, deadline, atomic.LoadUint32(&s.numWritten))
+				n, err := s.sess.writeFrameInternal(frame, deadline, 0)
 				atomic.AddUint32(&s.numWritten, uint32(sz))
 				sent += n
 				if err != nil {
diff --git a/vendor/modules.txt b/vendor/modules.txt
index 6ee3e06..6308e78 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -38,7 +38,7 @@ github.com/urfave/cli
 # github.com/xtaci/kcp-go/v5 v5.6.2
 ## explicit; go 1.13
 github.com/xtaci/kcp-go/v5
-# github.com/xtaci/smux v1.5.19
+# github.com/xtaci/smux v1.5.20
 ## explicit; go 1.13
 github.com/xtaci/smux
 # github.com/xtaci/tcpraw v1.2.25