diff --git a/src/Payload.php b/src/Payload.php
index eaf7d97..e077f00 100644
--- a/src/Payload.php
+++ b/src/Payload.php
@@ -11,7 +11,7 @@
  * The message can be consumed in chunks using the read() API, or it may be buffered and accessed in its entirety by
  * calling buffer(). Once buffering is requested through buffer(), the stream cannot be read in chunks.
  */
-class Payload implements ReadableStream
+final class Payload implements ReadableStream
 {
     private const MODE_STREAM = 1;
     private const MODE_BUFFER = 2;