diff --git a/jest/environment.js b/jest/environment.js
index a24f9f9ac42f8..a5ca53b7a948f 100644
--- a/jest/environment.js
+++ b/jest/environment.js
@@ -1,3 +1 @@
 __DEV__ = true;
-
-require.requireActual('../src/vendor/polyfill/Object.es6.js');
diff --git a/src/addons/transitions/ReactCSSTransitionGroup.js b/src/addons/transitions/ReactCSSTransitionGroup.js
index 6db897c88c0a3..2e4190c729fe2 100644
--- a/src/addons/transitions/ReactCSSTransitionGroup.js
+++ b/src/addons/transitions/ReactCSSTransitionGroup.js
@@ -14,6 +14,8 @@
 
 var React = require('React');
 
+var assign = require('Object.assign');
+
 var ReactTransitionGroup = React.createFactory(
   require('ReactTransitionGroup')
 );
@@ -54,7 +56,7 @@ var ReactCSSTransitionGroup = React.createClass({
   render: function() {
     return (
       ReactTransitionGroup(
-        Object.assign({}, this.props, {childFactory: this._wrapChild})
+        assign({}, this.props, {childFactory: this._wrapChild})
       )
     );
   }
diff --git a/src/addons/transitions/ReactTransitionGroup.js b/src/addons/transitions/ReactTransitionGroup.js
index 3cfec96318f88..ce967cff4c2c1 100644
--- a/src/addons/transitions/ReactTransitionGroup.js
+++ b/src/addons/transitions/ReactTransitionGroup.js
@@ -14,6 +14,7 @@
 var React = require('React');
 var ReactTransitionChildMapping = require('ReactTransitionChildMapping');
 
+var assign = require('Object.assign');
 var cloneWithProps = require('cloneWithProps');
 var emptyFunction = require('emptyFunction');
 
@@ -151,7 +152,7 @@ var ReactTransitionGroup = React.createClass({
       // This entered again before it fully left. Add it again.
       this.performEnter(key);
     } else {
-      var newChildren = Object.assign({}, this.state.children);
+      var newChildren = assign({}, this.state.children);
       delete newChildren[key];
       this.setState({children: newChildren});
     }
diff --git a/src/addons/update.js b/src/addons/update.js
index dded114ea41fd..34e078b20eb8d 100644
--- a/src/addons/update.js
+++ b/src/addons/update.js
@@ -11,6 +11,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var keyOf = require('keyOf');
 var invariant = require('invariant');
 
@@ -18,7 +19,7 @@ function shallowCopy(x) {
   if (Array.isArray(x)) {
     return x.concat();
   } else if (x && typeof x === 'object') {
-    return Object.assign(new x.constructor(), x);
+    return assign(new x.constructor(), x);
   } else {
     return x;
   }
@@ -98,7 +99,7 @@ function update(value, spec) {
       COMMAND_MERGE,
       nextValue
     );
-    Object.assign(nextValue, spec[COMMAND_MERGE]);
+    assign(nextValue, spec[COMMAND_MERGE]);
   }
 
   if (spec.hasOwnProperty(COMMAND_PUSH)) {
diff --git a/src/browser/ReactBrowserEventEmitter.js b/src/browser/ReactBrowserEventEmitter.js
index 7b957efca2f6d..f2c4a5dd783ea 100644
--- a/src/browser/ReactBrowserEventEmitter.js
+++ b/src/browser/ReactBrowserEventEmitter.js
@@ -18,6 +18,7 @@ var EventPluginRegistry = require('EventPluginRegistry');
 var ReactEventEmitterMixin = require('ReactEventEmitterMixin');
 var ViewportMetrics = require('ViewportMetrics');
 
+var assign = require('Object.assign');
 var isEventSupported = require('isEventSupported');
 
 /**
@@ -147,7 +148,7 @@ function getListeningForDocument(mountAt) {
  *
  * @internal
  */
-var ReactBrowserEventEmitter = Object.assign({}, ReactEventEmitterMixin, {
+var ReactBrowserEventEmitter = assign({}, ReactEventEmitterMixin, {
 
   /**
    * Injectable event backend
diff --git a/src/browser/ReactPutListenerQueue.js b/src/browser/ReactPutListenerQueue.js
index 2c8b2f6085d09..e47b6edcfe461 100644
--- a/src/browser/ReactPutListenerQueue.js
+++ b/src/browser/ReactPutListenerQueue.js
@@ -14,11 +14,13 @@
 var PooledClass = require('PooledClass');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 
+var assign = require('Object.assign');
+
 function ReactPutListenerQueue() {
   this.listenersToPut = [];
 }
 
-Object.assign(ReactPutListenerQueue.prototype, {
+assign(ReactPutListenerQueue.prototype, {
   enqueuePutListener: function(rootNodeID, propKey, propValue) {
     this.listenersToPut.push({
       rootNodeID: rootNodeID,
diff --git a/src/browser/ReactReconcileTransaction.js b/src/browser/ReactReconcileTransaction.js
index f777e4d12cec3..008890a256554 100644
--- a/src/browser/ReactReconcileTransaction.js
+++ b/src/browser/ReactReconcileTransaction.js
@@ -19,6 +19,8 @@ var ReactInputSelection = require('ReactInputSelection');
 var ReactPutListenerQueue = require('ReactPutListenerQueue');
 var Transaction = require('Transaction');
 
+var assign = require('Object.assign');
+
 /**
  * Ensures that, when possible, the selection range (currently selected text
  * input) is not disturbed by performing the transaction.
@@ -165,7 +167,7 @@ var Mixin = {
 };
 
 
-Object.assign(ReactReconcileTransaction.prototype, Transaction.Mixin, Mixin);
+assign(ReactReconcileTransaction.prototype, Transaction.Mixin, Mixin);
 
 PooledClass.addPoolingTo(ReactReconcileTransaction);
 
diff --git a/src/browser/ReactTextComponent.js b/src/browser/ReactTextComponent.js
index 4f0f20ff47d12..f87930f3f7479 100644
--- a/src/browser/ReactTextComponent.js
+++ b/src/browser/ReactTextComponent.js
@@ -16,6 +16,7 @@ var DOMPropertyOperations = require('DOMPropertyOperations');
 var ReactComponent = require('ReactComponent');
 var ReactElement = require('ReactElement');
 
+var assign = require('Object.assign');
 var escapeTextForBrowser = require('escapeTextForBrowser');
 
 /**
@@ -37,7 +38,7 @@ var ReactTextComponent = function(props) {
   // This constructor and it's argument is currently used by mocks.
 };
 
-Object.assign(ReactTextComponent.prototype, ReactComponent.Mixin, {
+assign(ReactTextComponent.prototype, ReactComponent.Mixin, {
 
   /**
    * Creates the markup for this text node. This node is not intended to have
diff --git a/src/browser/server/ReactServerRenderingTransaction.js b/src/browser/server/ReactServerRenderingTransaction.js
index 529ebec5e613c..7833b58831c60 100644
--- a/src/browser/server/ReactServerRenderingTransaction.js
+++ b/src/browser/server/ReactServerRenderingTransaction.js
@@ -17,6 +17,7 @@ var CallbackQueue = require('CallbackQueue');
 var ReactPutListenerQueue = require('ReactPutListenerQueue');
 var Transaction = require('Transaction');
 
+var assign = require('Object.assign');
 var emptyFunction = require('emptyFunction');
 
 /**
@@ -99,7 +100,7 @@ var Mixin = {
 };
 
 
-Object.assign(
+assign(
   ReactServerRenderingTransaction.prototype,
   Transaction.Mixin,
   Mixin
diff --git a/src/browser/syntheticEvents/SyntheticEvent.js b/src/browser/syntheticEvents/SyntheticEvent.js
index d603427743417..2d17e6cf9d51b 100644
--- a/src/browser/syntheticEvents/SyntheticEvent.js
+++ b/src/browser/syntheticEvents/SyntheticEvent.js
@@ -14,6 +14,7 @@
 
 var PooledClass = require('PooledClass');
 
+var assign = require('Object.assign');
 var emptyFunction = require('emptyFunction');
 var getEventTarget = require('getEventTarget');
 
@@ -82,7 +83,7 @@ function SyntheticEvent(dispatchConfig, dispatchMarker, nativeEvent) {
   this.isPropagationStopped = emptyFunction.thatReturnsFalse;
 }
 
-Object.assign(SyntheticEvent.prototype, {
+assign(SyntheticEvent.prototype, {
 
   preventDefault: function() {
     this.defaultPrevented = true;
@@ -140,11 +141,11 @@ SyntheticEvent.augmentClass = function(Class, Interface) {
   var Super = this;
 
   var prototype = Object.create(Super.prototype);
-  Object.assign(prototype, Class.prototype);
+  assign(prototype, Class.prototype);
   Class.prototype = prototype;
   Class.prototype.constructor = Class;
 
-  Class.Interface = Object.assign({}, Super.Interface, Interface);
+  Class.Interface = assign({}, Super.Interface, Interface);
   Class.augmentClass = Super.augmentClass;
 
   PooledClass.addPoolingTo(Class, PooledClass.threeArgumentPooler);
diff --git a/src/browser/ui/React.js b/src/browser/ui/React.js
index 382cc89f1d5e0..7031035d81160 100644
--- a/src/browser/ui/React.js
+++ b/src/browser/ui/React.js
@@ -11,10 +11,6 @@
 
 "use strict";
 
-// TODO: Move this elsewhere - it only exists in open source until a better
-// solution is found.
-require('Object.es6');
-
 var DOMPropertyOperations = require('DOMPropertyOperations');
 var EventPluginUtils = require('EventPluginUtils');
 var ReactChildren = require('ReactChildren');
@@ -36,6 +32,7 @@ var ReactPropTypes = require('ReactPropTypes');
 var ReactServerRendering = require('ReactServerRendering');
 var ReactTextComponent = require('ReactTextComponent');
 
+var assign = require('Object.assign');
 var deprecated = require('deprecated');
 var onlyChild = require('onlyChild');
 
@@ -84,6 +81,9 @@ var React = {
   isValidElement: ReactElement.isValidElement,
   withContext: ReactContext.withContext,
 
+  // Hook for JSX spread, don't use this for anything else.
+  __spread: assign,
+
   // Deprecations (remove for 0.13)
   renderComponent: deprecated(
     'React',
diff --git a/src/browser/ui/ReactDOMComponent.js b/src/browser/ui/ReactDOMComponent.js
index ba47058f3a39a..62fe8f0be97c9 100644
--- a/src/browser/ui/ReactDOMComponent.js
+++ b/src/browser/ui/ReactDOMComponent.js
@@ -22,6 +22,7 @@ var ReactMount = require('ReactMount');
 var ReactMultiChild = require('ReactMultiChild');
 var ReactPerf = require('ReactPerf');
 
+var assign = require('Object.assign');
 var escapeTextForBrowser = require('escapeTextForBrowser');
 var invariant = require('invariant');
 var isEventSupported = require('isEventSupported');
@@ -213,7 +214,7 @@ ReactDOMComponent.Mixin = {
       } else {
         if (propKey === STYLE) {
           if (propValue) {
-            propValue = props.style = Object.assign({}, props.style);
+            propValue = props.style = assign({}, props.style);
           }
           propValue = CSSPropertyOperations.createMarkupForStyles(propValue);
         }
@@ -362,7 +363,7 @@ ReactDOMComponent.Mixin = {
       }
       if (propKey === STYLE) {
         if (nextProp) {
-          nextProp = nextProps.style = Object.assign({}, nextProp);
+          nextProp = nextProps.style = assign({}, nextProp);
         }
         if (lastProp) {
           // Unset styles on `lastProp` but not on `nextProp`.
@@ -471,7 +472,7 @@ ReactDOMComponent.Mixin = {
 
 };
 
-Object.assign(
+assign(
   ReactDOMComponent.prototype,
   ReactComponent.Mixin,
   ReactDOMComponent.Mixin,
diff --git a/src/browser/ui/ReactEventListener.js b/src/browser/ui/ReactEventListener.js
index 9ea621d7d2623..e51fcd9c62f14 100644
--- a/src/browser/ui/ReactEventListener.js
+++ b/src/browser/ui/ReactEventListener.js
@@ -19,6 +19,7 @@ var ReactInstanceHandles = require('ReactInstanceHandles');
 var ReactMount = require('ReactMount');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
 var getEventTarget = require('getEventTarget');
 var getUnboundedScrollPosition = require('getUnboundedScrollPosition');
 
@@ -46,7 +47,7 @@ function TopLevelCallbackBookKeeping(topLevelType, nativeEvent) {
   this.nativeEvent = nativeEvent;
   this.ancestors = [];
 }
-Object.assign(TopLevelCallbackBookKeeping.prototype, {
+assign(TopLevelCallbackBookKeeping.prototype, {
   destructor: function() {
     this.topLevelType = null;
     this.nativeEvent = null;
diff --git a/src/browser/ui/__tests__/ReactDOMComponent-test.js b/src/browser/ui/__tests__/ReactDOMComponent-test.js
index 92c4b1f3732f3..2d54865dc3b78 100644
--- a/src/browser/ui/__tests__/ReactDOMComponent-test.js
+++ b/src/browser/ui/__tests__/ReactDOMComponent-test.js
@@ -13,6 +13,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var mocks = require('mocks');
 
 describe('ReactDOMComponent', function() {
@@ -223,7 +224,7 @@ describe('ReactDOMComponent', function() {
         this.props = initialProps || {};
         this._rootNodeID = 'test';
       };
-      Object.assign(NodeStub.prototype, ReactDOMComponent.Mixin);
+      assign(NodeStub.prototype, ReactDOMComponent.Mixin);
 
       genMarkup = function(props) {
         var transaction = new ReactReconcileTransaction();
@@ -273,7 +274,7 @@ describe('ReactDOMComponent', function() {
         this.props = initialProps || {};
         this._rootNodeID = 'test';
       };
-      Object.assign(NodeStub.prototype, ReactDOMComponent.Mixin);
+      assign(NodeStub.prototype, ReactDOMComponent.Mixin);
 
       genMarkup = function(props) {
         var transaction = new ReactReconcileTransaction();
@@ -310,9 +311,9 @@ describe('ReactDOMComponent', function() {
       var StubNativeComponent = function(element) {
         ReactComponent.Mixin.construct.call(this, element);
       };
-      Object.assign(StubNativeComponent.prototype, ReactComponent.Mixin);
-      Object.assign(StubNativeComponent.prototype, ReactDOMComponent.Mixin);
-      Object.assign(StubNativeComponent.prototype, ReactMultiChild.Mixin);
+      assign(StubNativeComponent.prototype, ReactComponent.Mixin);
+      assign(StubNativeComponent.prototype, ReactDOMComponent.Mixin);
+      assign(StubNativeComponent.prototype, ReactMultiChild.Mixin);
 
       mountComponent = function(props) {
         var transaction = new ReactReconcileTransaction();
diff --git a/src/browser/ui/dom/components/ReactDOMInput.js b/src/browser/ui/dom/components/ReactDOMInput.js
index 670e5de8af318..54ad741d98ebd 100644
--- a/src/browser/ui/dom/components/ReactDOMInput.js
+++ b/src/browser/ui/dom/components/ReactDOMInput.js
@@ -21,6 +21,7 @@ var ReactDOM = require('ReactDOM');
 var ReactMount = require('ReactMount');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 
 // Store a reference to the <input> `ReactDOMComponent`. TODO: use string
@@ -66,7 +67,7 @@ var ReactDOMInput = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = Object.assign({}, this.props);
+    var props = assign({}, this.props);
 
     props.defaultChecked = null;
     props.defaultValue = null;
diff --git a/src/browser/ui/dom/components/ReactDOMSelect.js b/src/browser/ui/dom/components/ReactDOMSelect.js
index 1b663b82841d2..5aba6d6f473e6 100644
--- a/src/browser/ui/dom/components/ReactDOMSelect.js
+++ b/src/browser/ui/dom/components/ReactDOMSelect.js
@@ -19,6 +19,8 @@ var ReactElement = require('ReactElement');
 var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
+
 // Store a reference to the <select> `ReactDOMComponent`. TODO: use string
 var select = ReactElement.createFactory(ReactDOM.select.type);
 
@@ -129,7 +131,7 @@ var ReactDOMSelect = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = Object.assign({}, this.props);
+    var props = assign({}, this.props);
 
     props.onChange = this._handleChange;
     props.value = null;
diff --git a/src/browser/ui/dom/components/ReactDOMTextarea.js b/src/browser/ui/dom/components/ReactDOMTextarea.js
index 0dbdadbc5e444..b2a53de9f632a 100644
--- a/src/browser/ui/dom/components/ReactDOMTextarea.js
+++ b/src/browser/ui/dom/components/ReactDOMTextarea.js
@@ -20,6 +20,7 @@ var ReactElement = require('ReactElement');
 var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 
 var warning = require('warning');
@@ -95,7 +96,7 @@ var ReactDOMTextarea = ReactCompositeComponent.createClass({
 
   render: function() {
     // Clone `this.props` so we don't mutate the input.
-    var props = Object.assign({}, this.props);
+    var props = assign({}, this.props);
 
     invariant(
       props.dangerouslySetInnerHTML == null,
diff --git a/src/core/ReactComponent.js b/src/core/ReactComponent.js
index aeb478d69b82f..bc9e0c01d5141 100644
--- a/src/core/ReactComponent.js
+++ b/src/core/ReactComponent.js
@@ -15,6 +15,7 @@ var ReactElement = require('ReactElement');
 var ReactOwner = require('ReactOwner');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 var keyMirror = require('keyMirror');
 
@@ -143,7 +144,7 @@ var ReactComponent = {
       // element props.
       var element = this._pendingElement || this._currentElement;
       this.replaceProps(
-        Object.assign({}, element.props, partialProps),
+        assign({}, element.props, partialProps),
         callback
       );
     },
@@ -192,7 +193,7 @@ var ReactComponent = {
       var element = this._pendingElement || this._currentElement;
       this._pendingElement = ReactElement.cloneAndReplaceProps(
         element,
-        Object.assign({}, element.props, partialProps)
+        assign({}, element.props, partialProps)
       );
       ReactUpdates.enqueueUpdate(this, callback);
     },
diff --git a/src/core/ReactCompositeComponent.js b/src/core/ReactCompositeComponent.js
index bbb276e6a00e3..1b063b9064e98 100644
--- a/src/core/ReactCompositeComponent.js
+++ b/src/core/ReactCompositeComponent.js
@@ -26,6 +26,7 @@ var ReactPropTypeLocations = require('ReactPropTypeLocations');
 var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
 var ReactUpdates = require('ReactUpdates');
 
+var assign = require('Object.assign');
 var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 var keyMirror = require('keyMirror');
@@ -340,7 +341,7 @@ var RESERVED_SPEC_KEYS = {
       childContextTypes,
       ReactPropTypeLocations.childContext
     );
-    Constructor.childContextTypes = Object.assign(
+    Constructor.childContextTypes = assign(
       {},
       Constructor.childContextTypes,
       childContextTypes
@@ -352,7 +353,7 @@ var RESERVED_SPEC_KEYS = {
       contextTypes,
       ReactPropTypeLocations.context
     );
-    Constructor.contextTypes = Object.assign(
+    Constructor.contextTypes = assign(
       {},
       Constructor.contextTypes,
       contextTypes
@@ -378,7 +379,7 @@ var RESERVED_SPEC_KEYS = {
       propTypes,
       ReactPropTypeLocations.prop
     );
-    Constructor.propTypes = Object.assign(
+    Constructor.propTypes = assign(
       {},
       Constructor.propTypes,
       propTypes
@@ -866,7 +867,7 @@ var ReactCompositeComponentMixin = {
     }
     // Merge with `_pendingState` if it exists, otherwise with existing state.
     this.replaceState(
-      Object.assign({}, this._pendingState || this.state, partialState),
+      assign({}, this._pendingState || this.state, partialState),
       callback
     );
   },
@@ -954,7 +955,7 @@ var ReactCompositeComponentMixin = {
           name
         );
       }
-      return Object.assign({}, currentContext, childContext);
+      return assign({}, currentContext, childContext);
     }
     return currentContext;
   },
@@ -1332,7 +1333,7 @@ var ReactCompositeComponentMixin = {
 };
 
 var ReactCompositeComponentBase = function() {};
-Object.assign(
+assign(
   ReactCompositeComponentBase.prototype,
   ReactComponent.Mixin,
   ReactOwner.Mixin,
diff --git a/src/core/ReactContext.js b/src/core/ReactContext.js
index bdfecfbedbdfc..67cb0e80b0ba3 100644
--- a/src/core/ReactContext.js
+++ b/src/core/ReactContext.js
@@ -11,6 +11,8 @@
 
 "use strict";
 
+var assign = require('Object.assign');
+
 /**
  * Keeps track of the current context.
  *
@@ -44,7 +46,7 @@ var ReactContext = {
   withContext: function(newContext, scopedCallback) {
     var result;
     var previousContext = ReactContext.current;
-    ReactContext.current = Object.assign({}, previousContext, newContext);
+    ReactContext.current = assign({}, previousContext, newContext);
     try {
       result = scopedCallback();
     } finally {
diff --git a/src/core/ReactDefaultBatchingStrategy.js b/src/core/ReactDefaultBatchingStrategy.js
index 41f455d72172b..9d1bd36392f0b 100644
--- a/src/core/ReactDefaultBatchingStrategy.js
+++ b/src/core/ReactDefaultBatchingStrategy.js
@@ -14,6 +14,7 @@
 var ReactUpdates = require('ReactUpdates');
 var Transaction = require('Transaction');
 
+var assign = require('Object.assign');
 var emptyFunction = require('emptyFunction');
 
 var RESET_BATCHED_UPDATES = {
@@ -34,7 +35,7 @@ function ReactDefaultBatchingStrategyTransaction() {
   this.reinitializeTransaction();
 }
 
-Object.assign(
+assign(
   ReactDefaultBatchingStrategyTransaction.prototype,
   Transaction.Mixin,
   {
diff --git a/src/core/ReactNativeComponent.js b/src/core/ReactNativeComponent.js
index c2e74d45078e1..ba485d614761a 100644
--- a/src/core/ReactNativeComponent.js
+++ b/src/core/ReactNativeComponent.js
@@ -11,6 +11,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 
 var genericComponentClass = null;
@@ -26,7 +27,7 @@ var ReactNativeComponentInjection = {
   // This accepts a keyed object with classes as values. Each key represents a
   // tag. That particular tag will use this class instead of the generic one.
   injectComponentClasses: function(componentClasses) {
-    Object.assign(tagToComponentClass, componentClasses);
+    assign(tagToComponentClass, componentClasses);
   }
 };
 
diff --git a/src/core/ReactPropTransferer.js b/src/core/ReactPropTransferer.js
index 5b34ffba598ac..ad2f93413d677 100644
--- a/src/core/ReactPropTransferer.js
+++ b/src/core/ReactPropTransferer.js
@@ -11,6 +11,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var emptyFunction = require('emptyFunction');
 var invariant = require('invariant');
 var joinClasses = require('joinClasses');
@@ -39,7 +40,7 @@ var transferStrategyMerge = createTransferStrategy(function(a, b) {
   // `merge` overrides the first object's (`props[key]` above) keys using the
   // second object's (`value`) keys. An object's style's existing `propA` would
   // get overridden. Flip the order here.
-  return Object.assign({}, b, a);
+  return assign({}, b, a);
 });
 
 /**
@@ -105,7 +106,7 @@ var ReactPropTransferer = {
    * @return {object} a new object containing both sets of props merged.
    */
   mergeProps: function(oldProps, newProps) {
-    return transferInto(Object.assign({}, oldProps), newProps);
+    return transferInto(assign({}, oldProps), newProps);
   },
 
   /**
diff --git a/src/core/ReactUpdates.js b/src/core/ReactUpdates.js
index 612ba816e2103..7486e3ac6742b 100644
--- a/src/core/ReactUpdates.js
+++ b/src/core/ReactUpdates.js
@@ -17,6 +17,7 @@ var ReactCurrentOwner = require('ReactCurrentOwner');
 var ReactPerf = require('ReactPerf');
 var Transaction = require('Transaction');
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 var warning = require('warning');
 
@@ -72,7 +73,7 @@ function ReactUpdatesFlushTransaction() {
     ReactUpdates.ReactReconcileTransaction.getPooled();
 }
 
-Object.assign(
+assign(
   ReactUpdatesFlushTransaction.prototype,
   Transaction.Mixin, {
   getTransactionWrappers: function() {
diff --git a/src/event/__tests__/EventPluginRegistry-test.js b/src/event/__tests__/EventPluginRegistry-test.js
index 139bc1a4746fe..8455e8f90590e 100644
--- a/src/event/__tests__/EventPluginRegistry-test.js
+++ b/src/event/__tests__/EventPluginRegistry-test.js
@@ -11,6 +11,8 @@
 
 "use strict";
 
+var assign = require('Object.assign');
+
 describe('EventPluginRegistry', function() {
   var EventPluginRegistry;
   var createPlugin;
@@ -20,7 +22,7 @@ describe('EventPluginRegistry', function() {
     EventPluginRegistry._resetEventPlugins();
 
     createPlugin = function(properties) {
-      return Object.assign({extractEvents: function() {}}, properties);
+      return assign({extractEvents: function() {}}, properties);
     };
   });
 
diff --git a/src/test/ReactDefaultPerfAnalysis.js b/src/test/ReactDefaultPerfAnalysis.js
index 5d2a246987fb2..57b6b957e3987 100644
--- a/src/test/ReactDefaultPerfAnalysis.js
+++ b/src/test/ReactDefaultPerfAnalysis.js
@@ -9,6 +9,8 @@
  * @providesModule ReactDefaultPerfAnalysis
  */
 
+var assign = require('Object.assign');
+
 // Don't try to save users less than 1.2ms (a number I made up)
 var DONT_CARE_THRESHOLD = 1.2;
 var DOM_OPERATION_TYPES = {
@@ -62,7 +64,7 @@ function getExclusiveSummary(measurements) {
 
   for (var i = 0; i < measurements.length; i++) {
     var measurement = measurements[i];
-    var allIDs = Object.assign(
+    var allIDs = assign(
       {},
       measurement.exclusive,
       measurement.inclusive
@@ -114,7 +116,7 @@ function getInclusiveSummary(measurements, onlyClean) {
 
   for (var i = 0; i < measurements.length; i++) {
     var measurement = measurements[i];
-    var allIDs = Object.assign(
+    var allIDs = assign(
       {},
       measurement.exclusive,
       measurement.inclusive
@@ -173,7 +175,7 @@ function getUnchangedComponents(measurement) {
   // the amount of time it took to render the entire subtree.
   var cleanComponents = {};
   var dirtyLeafIDs = Object.keys(measurement.writes);
-  var allIDs = Object.assign({}, measurement.exclusive, measurement.inclusive);
+  var allIDs = assign({}, measurement.exclusive, measurement.inclusive);
 
   for (var id in allIDs) {
     var isDirty = false;
diff --git a/src/test/ReactTestUtils.js b/src/test/ReactTestUtils.js
index 6af38c71f9812..43cf273ec69f5 100644
--- a/src/test/ReactTestUtils.js
+++ b/src/test/ReactTestUtils.js
@@ -22,6 +22,8 @@ var ReactTextComponent = require('ReactTextComponent');
 var ReactUpdates = require('ReactUpdates');
 var SyntheticEvent = require('SyntheticEvent');
 
+var assign = require('Object.assign');
+
 var topLevelTypes = EventConstants.topLevelTypes;
 
 function Event(suffix) {}
@@ -318,7 +320,7 @@ function makeSimulator(eventType) {
       ReactMount.getID(node),
       fakeNativeEvent
     );
-    Object.assign(event, eventData);
+    assign(event, eventData);
     EventPropagators.accumulateTwoPhaseDispatches(event);
 
     ReactUpdates.batchedUpdates(function() {
@@ -374,7 +376,7 @@ buildSimulators();
 function makeNativeSimulator(eventType) {
   return function(domComponentOrNode, nativeEventData) {
     var fakeNativeEvent = new Event(eventType);
-    Object.assign(fakeNativeEvent, nativeEventData);
+    assign(fakeNativeEvent, nativeEventData);
     if (ReactTestUtils.isDOMComponent(domComponentOrNode)) {
       ReactTestUtils.simulateNativeEventOnDOMComponent(
         eventType,
diff --git a/src/test/reactComponentExpect.js b/src/test/reactComponentExpect.js
index 00fd3581ef59b..c788682f65923 100644
--- a/src/test/reactComponentExpect.js
+++ b/src/test/reactComponentExpect.js
@@ -14,6 +14,8 @@
 
 var ReactTestUtils = require('ReactTestUtils');
 
+var assign = require('Object.assign');
+
 function reactComponentExpect(instance) {
   if (instance instanceof reactComponentExpect) {
     return instance;
@@ -29,7 +31,7 @@ function reactComponentExpect(instance) {
   expect(ReactTestUtils.isElement(instance)).toBe(false);
 }
 
-Object.assign(reactComponentExpect.prototype, {
+assign(reactComponentExpect.prototype, {
   // Getters -------------------------------------------------------------------
 
   /**
diff --git a/src/utils/CallbackQueue.js b/src/utils/CallbackQueue.js
index badb155d86b56..be51b7f57bfb5 100644
--- a/src/utils/CallbackQueue.js
+++ b/src/utils/CallbackQueue.js
@@ -13,6 +13,7 @@
 
 var PooledClass = require('PooledClass');
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 
 /**
@@ -31,7 +32,7 @@ function CallbackQueue() {
   this._contexts = null;
 }
 
-Object.assign(CallbackQueue.prototype, {
+assign(CallbackQueue.prototype, {
 
   /**
    * Enqueues a callback to be invoked when `notifyAll` is invoked.
diff --git a/src/utils/LegacyImmutableObject.js b/src/utils/LegacyImmutableObject.js
index 89d427c1230be..d83b58e23c0c0 100644
--- a/src/utils/LegacyImmutableObject.js
+++ b/src/utils/LegacyImmutableObject.js
@@ -12,6 +12,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 var isNode = require('isNode');
 var mergeHelpers = require('mergeHelpers');
@@ -42,7 +43,7 @@ if (__DEV__) {
    * @constructor
    */
   LegacyImmutableObject = function LegacyImmutableObject(initialProperties) {
-    Object.assign(this, initialProperties);
+    assign(this, initialProperties);
     deepFreeze(this);
   };
 
@@ -91,7 +92,7 @@ if (__DEV__) {
    */
   LegacyImmutableObject.set = function(immutableObject, put) {
     assertLegacyImmutableObject(immutableObject);
-    var totalNewFields = Object.assign({}, immutableObject, put);
+    var totalNewFields = assign({}, immutableObject, put);
     return new LegacyImmutableObject(totalNewFields);
   };
 
@@ -103,7 +104,7 @@ if (__DEV__) {
    * @constructor
    */
   LegacyImmutableObject = function LegacyImmutableObject(initialProperties) {
-    Object.assign(this, initialProperties);
+    assign(this, initialProperties);
   };
 
   /**
@@ -117,7 +118,7 @@ if (__DEV__) {
   LegacyImmutableObject.set = function(immutableObject, put) {
     assertLegacyImmutableObject(immutableObject);
     var newMap = new LegacyImmutableObject(immutableObject);
-    Object.assign(newMap, put);
+    assign(newMap, put);
     return newMap;
   };
 }
diff --git a/src/utils/OrderedMap.js b/src/utils/OrderedMap.js
index b083fb0eecc9b..59aa26ddb79b8 100644
--- a/src/utils/OrderedMap.js
+++ b/src/utils/OrderedMap.js
@@ -11,6 +11,7 @@
 
 "use strict";
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 
 var PREFIX = 'key:';
@@ -475,7 +476,7 @@ var OrderedMapMethods = {
   }
 };
 
-Object.assign(OrderedMapImpl.prototype, OrderedMapMethods);
+assign(OrderedMapImpl.prototype, OrderedMapMethods);
 
 var OrderedMap = {
   from: function(orderedMap) {
diff --git a/src/utils/__tests__/Transaction-test.js b/src/utils/__tests__/Transaction-test.js
index dfc6b50bf094e..ad9069f88c2ae 100644
--- a/src/utils/__tests__/Transaction-test.js
+++ b/src/utils/__tests__/Transaction-test.js
@@ -11,6 +11,8 @@
 
 "use strict";
 
+var assign = require('Object.assign');
+
 var Transaction;
 
 var INIT_ERRORED = 'initErrored';     // Just a dummy value to check for.
@@ -44,7 +46,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WON'T be set to something else
     };
-    Object.assign(TestTransaction.prototype, Transaction.Mixin);
+    assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -93,7 +95,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WILL be set to something else
     };
-    Object.assign(TestTransaction.prototype, Transaction.Mixin);
+    assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -154,7 +156,7 @@ describe('Transaction', function() {
       this.secondCloseParam = INIT_ERRORED;  // WILL be set to something else
       this.lastCloseParam = INIT_ERRORED;    // WILL be set to something else
     };
-    Object.assign(TestTransaction.prototype, Transaction.Mixin);
+    assign(TestTransaction.prototype, Transaction.Mixin);
     // Now, none of the close/inits throw, but the operation we wrap will throw.
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
@@ -218,7 +220,7 @@ describe('Transaction', function() {
     var TestTransaction = function() {
       this.reinitializeTransaction();
     };
-    Object.assign(TestTransaction.prototype, Transaction.Mixin);
+    assign(TestTransaction.prototype, Transaction.Mixin);
     var exceptionMsg = 'This exception should throw.';
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
@@ -247,7 +249,7 @@ describe('Transaction', function() {
       this.reinitializeTransaction();
       this.firstCloseParam = INIT_ERRORED; // WILL be set to something else
     };
-    Object.assign(TestTransaction.prototype, Transaction.Mixin);
+    assign(TestTransaction.prototype, Transaction.Mixin);
     TestTransaction.prototype.getTransactionWrappers = function() {
       return [
         {
@@ -275,7 +277,7 @@ describe('Transaction', function() {
     var NestedTransaction = function() {
       this.reinitializeTransaction();
     };
-    Object.assign(NestedTransaction.prototype, Transaction.Mixin);
+    assign(NestedTransaction.prototype, Transaction.Mixin);
     NestedTransaction.prototype.getTransactionWrappers = function() {
       return [{
         initialize: function() {
diff --git a/src/utils/deprecated.js b/src/utils/deprecated.js
index fe696e050cafd..2ac203492e5c5 100644
--- a/src/utils/deprecated.js
+++ b/src/utils/deprecated.js
@@ -9,6 +9,7 @@
  * @providesModule deprecated
  */
 
+var assign = require('Object.assign');
 var warning = require('warning');
 
 /**
@@ -37,7 +38,7 @@ function deprecated(namespace, oldName, newName, ctx, fn) {
     newFn.displayName = `${namespace}_${oldName}`;
     // We need to make sure all properties of the original fn are copied over.
     // In particular, this is needed to support PropTypes
-    return Object.assign(newFn, fn);
+    return assign(newFn, fn);
   }
 
   return fn;
diff --git a/src/vendor/core/emptyFunction.js b/src/vendor/core/emptyFunction.js
index 42b432a9cc0bf..b82329a4b1495 100644
--- a/src/vendor/core/emptyFunction.js
+++ b/src/vendor/core/emptyFunction.js
@@ -22,13 +22,11 @@ function makeEmptyFunction(arg) {
  */
 function emptyFunction() {}
 
-Object.assign(emptyFunction, {
-  thatReturns: makeEmptyFunction,
-  thatReturnsFalse: makeEmptyFunction(false),
-  thatReturnsTrue: makeEmptyFunction(true),
-  thatReturnsNull: makeEmptyFunction(null),
-  thatReturnsThis: function() { return this; },
-  thatReturnsArgument: function(arg) { return arg; }
-});
+emptyFunction.thatReturns = makeEmptyFunction;
+emptyFunction.thatReturnsFalse = makeEmptyFunction(false);
+emptyFunction.thatReturnsTrue = makeEmptyFunction(true);
+emptyFunction.thatReturnsNull = makeEmptyFunction(null);
+emptyFunction.thatReturnsThis = function() { return this; };
+emptyFunction.thatReturnsArgument = function(arg) { return arg; };
 
 module.exports = emptyFunction;
diff --git a/src/vendor/immutable/Immutable.js b/src/vendor/immutable/Immutable.js
index f7a2483b248a8..082c18d5b6362 100644
--- a/src/vendor/immutable/Immutable.js
+++ b/src/vendor/immutable/Immutable.js
@@ -9,6 +9,7 @@
  * @providesModule Immutable
  */
 
+var assign = require('Object.assign');
 var invariant = require('invariant');
 var isNode = require('isNode');
 var keyOf = require('keyOf');
@@ -59,7 +60,7 @@ class Immutable {
   static mergeAllPropertiesInto(destination, propertyObjects) {
     var argLength = propertyObjects.length;
     for (var i = 0; i < argLength; i++) {
-      Object.assign(destination, propertyObjects[i]);
+      assign(destination, propertyObjects[i]);
     }
   }
 
diff --git a/src/vendor/polyfill/Object.es6.js b/src/vendor/polyfill/Object.es6.js
deleted file mode 100644
index f94b8b2a68bbd..0000000000000
--- a/src/vendor/polyfill/Object.es6.js
+++ /dev/null
@@ -1,45 +0,0 @@
-/**
- * Copyright 2014, Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- *
- * @providesModule Object.es6
- * @polyfill
- */
-
-// https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.assign
-
-if (!Object.assign) {
-  Object.assign = function(target, sources) {
-    if (target == null) {
-      throw new TypeError('Object.assign target cannot be null or undefined');
-    }
-
-    var to = Object(target);
-    var hasOwnProperty = Object.prototype.hasOwnProperty;
-
-    for (var nextIndex = 1; nextIndex < arguments.length; nextIndex++) {
-      var nextSource = arguments[nextIndex];
-      if (nextSource == null) {
-        continue;
-      }
-
-      var from = Object(nextSource);
-
-      // We don't currently support accessors nor proxies. Therefore this
-      // copy cannot throw. If we ever supported this then we must handle
-      // exceptions and side-effects.
-
-      for (var key in from) {
-        if (hasOwnProperty.call(from, key)) {
-          to[key] = from[key];
-        }
-      }
-    }
-
-    return to;
-  };
-}
diff --git a/src/vendor/stubs/Object.assign.js b/src/vendor/stubs/Object.assign.js
new file mode 100644
index 0000000000000..bffdee93d1a81
--- /dev/null
+++ b/src/vendor/stubs/Object.assign.js
@@ -0,0 +1,57 @@
+/**
+ * Copyright 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule Object.assign
+ */
+
+// This is an optimized version that fails on hasOwnProperty checks
+// and non objects. It's not spec-compliant. It's a perf optimization.
+
+var hasOwnProperty = Object.prototype.hasOwnProperty;
+
+function assign(target, sources) {
+  if (__DEV__) {
+    if (target == null) {
+      throw new TypeError('Object.assign target cannot be null or undefined');
+    }
+    if (typeof target !== 'object' && typeof target !== 'function') {
+      throw new TypeError(
+        'In this environment the target of assign MUST be an object. ' +
+        'This error is a performance optimization and not spec compliant.'
+      );
+    }
+  }
+
+  for (var nextIndex = 1; nextIndex < arguments.length; nextIndex++) {
+    var nextSource = arguments[nextIndex];
+    if (nextSource == null) {
+      continue;
+    }
+
+    // We don't currently support accessors nor proxies. Therefore this
+    // copy cannot throw. If we ever supported this then we must handle
+    // exceptions and side-effects.
+
+    for (var key in nextSource) {
+      if (__DEV__) {
+        if (!hasOwnProperty.call(nextSource, key)) {
+          throw new TypeError(
+            'One of the sources to assign has an enumerable key on the ' +
+            'prototype chain. This is an edge case that we do not support. ' +
+            'This error is a performance optimization and not spec compliant.'
+          );
+        }
+      }
+      target[key] = nextSource[key];
+    }
+  }
+
+  return target;
+};
+
+module.exports = assign;
diff --git a/src/vendor_deprecated/core/merge.js b/src/vendor_deprecated/core/merge.js
index 389b335bb91d9..30d00097f2752 100644
--- a/src/vendor_deprecated/core/merge.js
+++ b/src/vendor_deprecated/core/merge.js
@@ -11,6 +11,8 @@
 
 "use strict";
 
+var assign = require('Object.assign');
+
 /**
  * Shallow merges two structures into a return value, without mutating either.
  *
@@ -19,7 +21,7 @@
  * @return {object} The shallow extension of one by two.
  */
 var merge = function(one, two) {
-  return Object.assign({}, one, two);
+  return assign({}, one, two);
 };
 
 module.exports = merge;
diff --git a/src/vendor_deprecated/core/mergeInto.js b/src/vendor_deprecated/core/mergeInto.js
index 7bf424aacec79..842d6a5ea4c77 100644
--- a/src/vendor_deprecated/core/mergeInto.js
+++ b/src/vendor_deprecated/core/mergeInto.js
@@ -12,7 +12,9 @@
 
 "use strict";
 
-module.exports = Object.assign;
+var assign = require('Object.assign');
+
+module.exports = assign;
 
 // deprecation notice
 console.warn(
diff --git a/vendor/fbtransform/transforms/__tests__/react-test.js b/vendor/fbtransform/transforms/__tests__/react-test.js
index efa9da984d9ee..1b76be8f3c386 100644
--- a/vendor/fbtransform/transforms/__tests__/react-test.js
+++ b/vendor/fbtransform/transforms/__tests__/react-test.js
@@ -42,7 +42,7 @@ describe('react jsx', function() {
     var Component = jest.genMockFunction();
     var Child = jest.genMockFunction();
     var objectAssignMock = jest.genMockFunction();
-    Object.assign = objectAssignMock;
+    React.__spread = objectAssignMock;
     eval(transform(code).code);
     return expect(objectAssignMock);
   }
@@ -309,12 +309,12 @@ describe('react jsx', function() {
     expect(() => transform(code)).toThrow();
   });
 
-  it('wraps props in Object.assign for spread attributes', function() {
+  it('wraps props in React.__spread for spread attributes', function() {
     var code =
       '<Component { ... x } y\n' +
       '={2 } z />';
     var result =
-      'React.createElement(Component, Object.assign({},    x , {y: \n' +
+      'React.createElement(Component, React.__spread({},    x , {y: \n' +
       '2, z: true}))';
 
     expect(transform(code).code).toBe(result);
@@ -326,7 +326,7 @@ describe('react jsx', function() {
       '  {...this.props}\n' +
       '  sound="moo" />';
     var result =
-      'React.createElement(Component, Object.assign({}, \n' +
+      'React.createElement(Component, React.__spread({}, \n' +
       '  this.props, \n' +
       '  {sound: "moo"}))';
 
@@ -340,7 +340,7 @@ describe('react jsx', function() {
     expect(transform(code).code).toBe(result);
   });
 
-  it('does not call Object.assign when there are no spreads', function() {
+  it('does not call React.__spread when there are no spreads', function() {
     expectObjectAssign(
       '<Component x={y} />'
     ).not.toBeCalled();
@@ -376,13 +376,13 @@ describe('react jsx', function() {
     ).toBeCalledWith({x: 1}, y);
   });
 
-  it('passes the same value multiple times to Object.assign', function() {
+  it('passes the same value multiple times to React.__spread', function() {
     expectObjectAssign(
       '<Component x={1} y="2" {...z} {...z}><Child /></Component>'
     ).toBeCalledWith({x: 1, y: "2"}, z, z);
   });
 
-  it('evaluates sequences before passing them to Object.assign', function() {
+  it('evaluates sequences before passing them to React.__spread', function() {
     expectObjectAssign(
       '<Component x="1" {...(z = { y: 2 }, z)} z={3}>Text</Component>'
     ).toBeCalledWith({x: "1"}, { y: 2 }, {z: 3});
diff --git a/vendor/fbtransform/transforms/react.js b/vendor/fbtransform/transforms/react.js
index c1625d3209ba2..3de4f6c2679a7 100644
--- a/vendor/fbtransform/transforms/react.js
+++ b/vendor/fbtransform/transforms/react.js
@@ -89,7 +89,7 @@ function visitReactTag(traverse, object, path, state) {
 
   // if we don't have any attributes, pass in null
   if (hasAtLeastOneSpreadProperty) {
-    utils.append('Object.assign({', state);
+    utils.append('React.__spread({', state);
   } else if (hasAttributes) {
     utils.append('{', state);
   } else {