diff --git a/transport/xhttp/config.go b/transport/xhttp/config.go
index 3d97a24e..f6bf572e 100644
--- a/transport/xhttp/config.go
+++ b/transport/xhttp/config.go
@@ -630,7 +630,7 @@ func (c *Config) GetGenerateSessionID() (func() string, error) {
 		if err != nil {
 			return nil, fmt.Errorf("invalid session-length: %w", err)
 		}
-		room := roomSize(len(c.SessionTable), sessionLength.Min, sessionLength.Max)
+		room := roomSize(len(sessionTable), sessionLength.Min, sessionLength.Max)
 		// 2.1B possiblities should be enough
 		if room.Cmp(big.NewInt(2<<30)) < 0 {
 			return nil, errors.New("session-table or session-length is too small")