Fixed lint errors
diff --git a/src/node/index.js b/src/node/index.js
index 1bef207..4b5302e 100644
--- a/src/node/index.js
+++ b/src/node/index.js
@@ -31,6 +31,8 @@
  *
  */
 
+'use strict';
+
 var _ = require('underscore');
 
 var ProtoBuf = require('protobufjs');