diff --git a/build.js b/build.js
index ca137e8..28a27eb 100644
--- a/build.js
+++ b/build.js
@@ -1,3 +1,4 @@
+"use strict";
 var stealTools = require("steal-tools");
 
 stealTools.export({
diff --git a/compat.js b/compat.js
index 792cf33..3ae2acb 100644
--- a/compat.js
+++ b/compat.js
@@ -1,3 +1,4 @@
+"use strict";
 var addEventCompat = require('can-dom-events/helpers/add-event-compat');
 var radioChange = require('./can-event-dom-radiochange');