diff --git a/lib/mixins/element-mixin.html b/lib/mixins/element-mixin.html
index 06a886b893..2fed46d2b8 100644
--- a/lib/mixins/element-mixin.html
+++ b/lib/mixins/element-mixin.html
@@ -231,11 +231,8 @@
       if (info.observer) {
         proto._createPropertyObserver(name, info.observer, allProps[info.observer]);
       }
-      // always ensure an accessor is made for properties but don't stomp
-      // on existing values.
-      if (!info.readOnly && !(name in proto)) {
-        proto._createPropertyAccessor(name);
-      }
+      // always create the mapping from attribute back to property for deserialization.
+      proto._addPropertyToAttributeMap(name);
     }
 
     /**
diff --git a/lib/mixins/properties-changed.html b/lib/mixins/properties-changed.html
index baf7383d35..aca31674af 100644
--- a/lib/mixins/properties-changed.html
+++ b/lib/mixins/properties-changed.html
@@ -105,17 +105,30 @@
          * @protected
          */
         _createPropertyAccessor(property, readOnly) {
+          this._addPropertyToAttributeMap(property);
           if (!this.hasOwnProperty('__dataHasAccessor')) {
             this.__dataHasAccessor = Object.assign({}, this.__dataHasAccessor);
           }
+          if (!this.__dataHasAccessor[property]) {
+            this.__dataHasAccessor[property] = true;
+            this._definePropertyAccessor(property, readOnly);
+          }
+        }
+
+        /**
+         * Adds the given `property` to a map matching attribute names
+         * to property names, using `attributeNameForProperty`. This map is
+         * used when deserializing attribute values to properties.
+         *
+         * @param {string} property Name of the property
+         */
+        _addPropertyToAttributeMap(property) {
           if (!this.hasOwnProperty('__dataAttributes')) {
             this.__dataAttributes = Object.assign({}, this.__dataAttributes);
           }
-          if (!this.__dataHasAccessor[property]) {
-            this.__dataHasAccessor[property] = true;
+          if (!this.__dataAttributes[property]) {
             const attr = this.constructor.attributeNameForProperty(property);
             this.__dataAttributes[attr] = property;
-            this._definePropertyAccessor(property, readOnly);
           }
         }
 
diff --git a/test/unit/polymer.element.html b/test/unit/polymer.element.html
index d8f6ccf8c8..3f098da0d9 100644
--- a/test/unit/polymer.element.html
+++ b/test/unit/polymer.element.html
@@ -389,23 +389,6 @@ <h1>Sub template</h1>
       assert.equal(el.computedProp, true);
     });
 
-    test('properties have accessors', function() {
-      assert.isTrue(el.__dataHasAccessor.accessor);
-      el._propertiesChanged = sinon.spy();
-      el.accessor = 'hi';
-      assert.equal(el._propertiesChanged.args[0][0].accessor, 'hi');
-    });
-
-    test('properties with no effects do not stomp existing accessors', function() {
-      assert.notOk(el.__dataHasAccessor.noStomp);
-      el._propertiesChanged = sinon.spy();
-      el.accessor = 'hi';
-      el.noStomp = 'hi';
-      const props = el._propertiesChanged.args[0][0];
-      assert.equal(props.accessor, 'hi');
-      assert.notOk(props.noStomp);
-    });
-
     test('attributes', function() {
       const fixtureEl = fixture('my-element-attr');
       assert.equal(fixtureEl.prop, 'attr');