diff --git a/bower.json b/bower.json
index 1181b64c18..434ce7e1f2 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "polymer",
-  "version": "2.0.0-rc.2",
+  "version": "2.0.0-rc.3",
   "main": [
     "polymer.html"
   ],
diff --git a/lib/legacy/class.html b/lib/legacy/class.html
index ea8dfd835e..108e3d1f4f 100644
--- a/lib/legacy/class.html
+++ b/lib/legacy/class.html
@@ -25,11 +25,7 @@
       registered: true,
       attributeChanged: true,
       // meta objects
-      behaviors: true,
-      hostAttributes: true,
-      properties: true,
-      observers: true,
-      listeners: true
+      behaviors: true
     }
 
     /**
@@ -135,8 +131,6 @@
 
     function GenerateClassFromInfo(info, Base) {
 
-      let registered = false;
-
       class PolymerGenerated extends Base {
 
         static get properties() {
@@ -167,13 +161,9 @@
         }
 
         _registered() {
-          if (!registered) {
-            super._registered();
-            // call `registered` only if it was not called for *this* constructor
-            registered = true;
-            if (info.registered) {
-              info.registered.call(Object.getPrototypeOf(this));
-            }
+          super._registered();
+          if (info.registered) {
+            info.registered.call(Object.getPrototypeOf(this));
           }
         }
 
diff --git a/lib/legacy/legacy-element-mixin.html b/lib/legacy/legacy-element-mixin.html
index 6de979f229..73f087ad04 100644
--- a/lib/legacy/legacy-element-mixin.html
+++ b/lib/legacy/legacy-element-mixin.html
@@ -106,12 +106,17 @@
 
       /**
        * Overrides the default `Polymer.PropertyEffects` implementation to
-       * add support for one-time `registration` callback.
+       * add support for class initialization via the `_registered` callback.
+       * This is called only when the first instance of the element is created.
        *
        * @override
        */
       _initializeProperties() {
-        this._registered();
+        let proto = Object.getPrototypeOf(this);
+        if (!proto.hasOwnProperty('__hasRegisterFinished')) {
+          proto.__hasRegisterFinished = true;
+          this._registered();
+        }
         super._initializeProperties();
       }
 
diff --git a/lib/utils/mixin.html b/lib/utils/mixin.html
index 91dbdbfec7..85a04b0e3a 100644
--- a/lib/utils/mixin.html
+++ b/lib/utils/mixin.html
@@ -51,9 +51,7 @@
   Polymer.dedupingMixin = function(mixin) {
     mixin = cachingMixin(mixin);
     // maintain a unique id for each mixin
-    if (!mixin.__id) {
-      mixin.__dedupeId = ++dedupeId;
-    }
+    mixin.__dedupeId = ++dedupeId;
     return function(base) {
       let baseSet = base.__mixinSet;
       if (baseSet && baseSet[mixin.__dedupeId]) {
diff --git a/package.json b/package.json
index 57eb6235f4..5abd923fb5 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polymer/polymer",
-  "version": "2.0.0-rc.2",
+  "version": "2.0.0-rc.3",
   "description": "The Polymer library makes it easy to create your own web components. Give your element some markup and properties, and then use it on a site. Polymer provides features like dynamic templates and data binding to reduce the amount of boilerplate you need to write",
   "main": "polymer.html",
   "directories": {
diff --git a/test/unit/behaviors.html b/test/unit/behaviors.html
index 27535891e3..997a6ded74 100644
--- a/test/unit/behaviors.html
+++ b/test/unit/behaviors.html
@@ -172,7 +172,12 @@
 
       behaviors: [
         Polymer.BehaviorA
-      ]
+      ],
+
+      properties: {},
+      observers: [],
+      hostAttributes: {},
+      listeners: {}
     });
 
     Polymer({
@@ -307,6 +312,14 @@
     assert.equal(el.is, 'single-behavior');
   });
 
+  test('instance behaviors, properties, observers, hostAttributes, listeners', function() {
+    assert.isOk(el.behaviors);
+    assert.isOk(el.properties);
+    assert.isOk(el.observers);
+    assert.isOk(el.hostAttributes);
+    assert.isOk(el.listeners);
+  });
+
   test('ready from behavior', function() {
     assert.equal(el.__readyA, true);
   });
diff --git a/test/unit/mixin-behaviors.html b/test/unit/mixin-behaviors.html
index e64ee2ae24..8bfd9dbfe1 100644
--- a/test/unit/mixin-behaviors.html
+++ b/test/unit/mixin-behaviors.html
@@ -329,12 +329,18 @@
       BehaviorRegistered.prototype.registeredCount = 0;
 
       customElements.define(BehaviorRegistered.is, BehaviorRegistered);
+
+      class BehaviorRegisteredExt extends BehaviorRegistered {
+        static get is() { return 'behavior-registered-ext'}
+      }
+
+      BehaviorRegisteredExt.prototype.registeredCount = 0;
+
+      customElements.define(BehaviorRegisteredExt.is, BehaviorRegisteredExt);
     });
     </script>
   </dom-module>
 
-  </script>
-
   <test-fixture id="single">
     <template>
       <single-behavior></single-behavior>
@@ -364,6 +370,12 @@
       <behavior-registered></behavior-registered>
     </template>
   </test-fixture>
+
+  <test-fixture id="registered-ext">
+    <template>
+      <behavior-registered-ext></behavior-registered-ext>
+    </template>
+  </test-fixture>
 <script>
 
 suite('single behavior element', function() {
@@ -421,6 +433,14 @@
     assert.deepEqual(el.registeredProps, [true, true, true]);
   });
 
+  test('extending element with behaviors with registered properly registers', function() {
+    var el = fixture('registered-ext');
+    assert.equal(el.registeredCount, 4);
+    assert.equal(el.registeredBehaviors.length, 3);
+    assert.equal(el.registeredBehaviors, el.behaviors);
+    assert.deepEqual(el.registeredProps, [true, true, true]);
+  });
+
 });
 
 suite('behavior lifecycle', function() {