diff --git a/src/lib/base.html b/src/lib/base.html
index 675bacb0d3..3ce0612000 100644
--- a/src/lib/base.html
+++ b/src/lib/base.html
@@ -57,9 +57,9 @@
     },
 
     // reserved for canonical behavior
-    attributeChangedCallback: function(name) {
+    attributeChangedCallback: function(name, oldValue, newValue) {
       this._attributeChangedImpl(name); // abstract
-      this._doBehavior('attributeChanged', arguments); // abstract
+      this._doBehavior('attributeChanged', [name, oldValue, newValue]); // abstract
     },
 
     _attributeChangedImpl: function(name) {
diff --git a/src/standard/events.html b/src/standard/events.html
index 3e1cd3a22f..ccaf5f8432 100644
--- a/src/standard/events.html
+++ b/src/standard/events.html
@@ -56,7 +56,7 @@
     listeners: {},
 
     _listenListeners: function(listeners) {
-      for (eventName in listeners) {
+      for (var eventName in listeners) {
         this.listen(this, eventName, listeners[eventName]);
       }
     },