diff --git a/index.js b/index.js
index f2122e0..477c145 100644
--- a/index.js
+++ b/index.js
@@ -1,3 +1,4 @@
+'use strict'
 var attrToProp = require('hyperscript-attribute-to-property')
 
 var VAR = 0, TEXT = 1, OPEN = 2, CLOSE = 3, ATTR = 4