diff --git a/lib/_stream_wrap.js b/lib/_stream_wrap.js
index c3dcfe51b6c..1eac2ddf941 100644
--- a/lib/_stream_wrap.js
+++ b/lib/_stream_wrap.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const util = require('util');
 const Socket = require('net').Socket;
 const JSStream = process.binding('js_stream').JSStream;