diff --git a/index.js b/index.js
index a6d9f1a..9d61a2f 100644
--- a/index.js
+++ b/index.js
@@ -26,6 +26,7 @@ module.exports = function bufferStream() {
 	}
 
 	return {
+		_promistreamVersion: 0,
 		description: "buffer stream",
 		abort: propagateAbort,
 		peek: function peekValue_bufferedSourceStream(source) {