diff --git a/lib/index.js b/lib/index.js
index 6d1e039..52b4835 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -12,9 +12,11 @@ var stampit = require('stampit');
 var _ = require('lodash');
 var EventEmitter = require('events').EventEmitter;
 
-var AssignFirstArgument = stampit({ init(opts) {
-  Object.assign(this, opts);
-}});
+var AssignFirstArgument = stampit({
+  init: function init(opts) {
+    Object.assign(this, opts);
+  }
+});
 
 var StateMachine = stampit({
   props: {