diff --git a/gbn/config.go b/gbn/config.go
index 4d14f7f..20dbd8c 100644
--- a/gbn/config.go
+++ b/gbn/config.go
@@ -45,6 +45,8 @@ type config struct {
 
 	pingTime time.Duration
 	pongTime time.Duration
+
+	onFIN func()
 }
 
 // newConfig constructs a new config struct.
diff --git a/gbn/gbn_conn.go b/gbn/gbn_conn.go
index 92c97d2..1709f9f 100644
--- a/gbn/gbn_conn.go
+++ b/gbn/gbn_conn.go
@@ -646,6 +646,10 @@ func (g *GoBackNConn) receivePacketsForever() error { // nolint:gocyclo
 
 			close(g.remoteClosed)
 
+			if g.cfg.onFIN != nil {
+				g.cfg.onFIN()
+			}
+
 			return errTransportClosing
 
 		default:
diff --git a/gbn/options.go b/gbn/options.go
index 2c1e8df..9aedd27 100644
--- a/gbn/options.go
+++ b/gbn/options.go
@@ -4,6 +4,12 @@ import "time"
 
 type Option func(conn *config)
 
+func WithOnFIN(fn func()) Option {
+	return func(conn *config) {
+		conn.onFIN = fn
+	}
+}
+
 // WithMaxSendSize is used to set the maximum payload size in bytes per packet.
 // If set and a large payload comes through then it will be split up into
 // multiple packets with payloads no larger than the given maximum size.
diff --git a/mailbox/client_conn.go b/mailbox/client_conn.go
index 6355a94..784d60c 100644
--- a/mailbox/client_conn.go
+++ b/mailbox/client_conn.go
@@ -157,20 +157,25 @@ func NewClientConn(ctx context.Context, sid [64]byte, serverHost string,
 	}
 
 	c := &ClientConn{
-		transport: transport,
-		gbnOptions: []gbn.Option{
-			gbn.WithTimeout(gbnTimeout),
-			gbn.WithHandshakeTimeout(gbnHandshakeTimeout),
-			gbn.WithKeepalivePing(
-				gbnClientPingTimeout, gbnPongTimeout,
-			),
-		},
+		transport:   transport,
 		status:      ClientStatusNotConnected,
 		onNewStatus: onNewStatus,
 		quit:        make(chan struct{}),
 		cancel:      cancel,
 		log:         logger,
 	}
+
+	c.gbnOptions = []gbn.Option{
+		gbn.WithTimeout(gbnTimeout),
+		gbn.WithHandshakeTimeout(gbnHandshakeTimeout),
+		gbn.WithKeepalivePing(
+			gbnClientPingTimeout, gbnPongTimeout,
+		),
+		gbn.WithOnFIN(func() {
+			c.setStatus(ClientStatusSessionNotFound)
+		}),
+	}
+
 	c.connKit = &connKit{
 		ctx:        ctxc,
 		impl:       c,