diff --git a/serverstream.go b/serverstream.go
index fdc68603..95bf363b 100644
--- a/serverstream.go
+++ b/serverstream.go
@@ -35,6 +35,7 @@ type ServerStream struct {
 	activeUnicastReaders map[*ServerSession]struct{}
 	readers              map[*ServerSession]struct{}
 	streamTracks         []*serverStreamTrack
+	closed               bool
 }
 
 // NewServerStream allocates a ServerStream.
@@ -59,7 +60,8 @@ func NewServerStream(tracks Tracks) *ServerStream {
 // Close closes a ServerStream.
 func (st *ServerStream) Close() error {
 	st.mutex.Lock()
-	defer st.mutex.Unlock()
+	st.closed = true
+	st.mutex.Unlock()
 
 	for ss := range st.readers {
 		ss.Close()
@@ -71,8 +73,6 @@ func (st *ServerStream) Close() error {
 		}
 	}
 
-	st.readers = nil
-
 	return nil
 }
 
@@ -119,12 +119,33 @@ func (st *ServerStream) readerAdd(
 	st.mutex.Lock()
 	defer st.mutex.Unlock()
 
-	if st.readers == nil {
+	if st.closed {
 		return fmt.Errorf("stream is closed")
 	}
 
-	// check whether UDP ports are already assigned to another reader
-	if transport == TransportUDP {
+	if st.s == nil {
+		st.s = ss.s
+
+		for trackID, track := range st.streamTracks {
+			// always generate RTCP sender reports.
+			// they're mandatory when transport protocol is UDP or UDP-multicast.
+			// they're also needed when transport protocol is TCP and client is Nvidia Deepstream
+			// since they're used to compute NTP timestamp of frames:
+			// https://docs.nvidia.com/metropolis/deepstream/dev-guide/text/DS_NTP_Timestamp.html
+			cTrackID := trackID
+			track.rtcpSender = rtcpsender.New(
+				st.s.udpSenderReportPeriod,
+				st.tracks[trackID].ClockRate(),
+				func(pkt rtcp.Packet) {
+					st.WritePacketRTCP(cTrackID, pkt)
+				},
+			)
+		}
+	}
+
+	switch transport {
+	case TransportUDP:
+		// check whether UDP ports are already assigned to another reader
 		for r := range st.readers {
 			if *r.setuppedTransport == TransportUDP &&
 				r.author.ip().Equal(ss.author.ip()) &&
@@ -136,31 +157,9 @@ func (st *ServerStream) readerAdd(
 				}
 			}
 		}
-	}
 
-	if st.s == nil {
-		st.s = ss.s
-
-		for trackID, track := range st.streamTracks {
-			cTrackID := trackID
-
-			// always generate RTCP sender reports.
-			// they're mandatory when transport protocol is UDP or UDP-multicast.
-			// they're also needed when transport protocol is TCP and client is Nvidia Deepstream
-			// since they're used to compute NTP timestamp of frames:
-			// https://docs.nvidia.com/metropolis/deepstream/dev-guide/text/DS_NTP_Timestamp.html
-			track.rtcpSender = rtcpsender.New(
-				st.s.udpSenderReportPeriod,
-				st.tracks[trackID].ClockRate(),
-				func(pkt rtcp.Packet) {
-					st.WritePacketRTCP(cTrackID, pkt)
-				},
-			)
-		}
-	}
-
-	// allocate multicast listeners
-	if transport == TransportUDPMulticast {
+	case TransportUDPMulticast:
+		// allocate multicast listeners
 		for _, track := range st.streamTracks {
 			if track.multicastHandler == nil {
 				mh, err := newServerMulticastHandler(st.s)
@@ -181,6 +180,10 @@ func (st *ServerStream) readerRemove(ss *ServerSession) {
 	st.mutex.Lock()
 	defer st.mutex.Unlock()
 
+	if st.closed {
+		return
+	}
+
 	delete(st.readers, ss)
 
 	if len(st.readers) == 0 {
@@ -197,6 +200,10 @@ func (st *ServerStream) readerSetActive(ss *ServerSession) {
 	st.mutex.Lock()
 	defer st.mutex.Unlock()
 
+	if st.closed {
+		return
+	}
+
 	if *ss.setuppedTransport == TransportUDPMulticast {
 		for trackID, track := range ss.setuppedTracks {
 			st.streamTracks[trackID].multicastHandler.rtcpl.addClient(
@@ -211,6 +218,10 @@ func (st *ServerStream) readerSetInactive(ss *ServerSession) {
 	st.mutex.Lock()
 	defer st.mutex.Unlock()
 
+	if st.closed {
+		return
+	}
+
 	if *ss.setuppedTransport == TransportUDPMulticast {
 		for trackID := range ss.setuppedTracks {
 			st.streamTracks[trackID].multicastHandler.rtcpl.removeClient(ss)
@@ -232,6 +243,10 @@ func (st *ServerStream) WritePacketRTP(trackID int, pkt *rtp.Packet, ptsEqualsDT
 	st.mutex.RLock()
 	defer st.mutex.RUnlock()
 
+	if st.closed {
+		return
+	}
+
 	track := st.streamTracks[trackID]
 	now := time.Now()
 
@@ -269,6 +284,10 @@ func (st *ServerStream) WritePacketRTCP(trackID int, pkt rtcp.Packet) {
 	st.mutex.RLock()
 	defer st.mutex.RUnlock()
 
+	if st.closed {
+		return
+	}
+
 	// send unicast
 	for r := range st.activeUnicastReaders {
 		r.writePacketRTCP(trackID, byts)