diff --git a/src/isomorphic/classic/element/ReactElement.js b/src/isomorphic/classic/element/ReactElement.js
index 42b7e37cab3bb..9e333270e2f5c 100644
--- a/src/isomorphic/classic/element/ReactElement.js
+++ b/src/isomorphic/classic/element/ReactElement.js
@@ -14,71 +14,12 @@
 var ReactCurrentOwner = require('ReactCurrentOwner');
 
 var assign = require('Object.assign');
-var warning = require('warning');
 
 var RESERVED_PROPS = {
   key: true,
   ref: true,
 };
 
-/**
- * Warn for mutations.
- *
- * @internal
- * @param {object} object
- * @param {string} key
- */
-function defineWarningProperty(object, key) {
-  Object.defineProperty(object, key, {
-
-    configurable: false,
-    enumerable: true,
-
-    get: function() {
-      if (!this._store) {
-        return null;
-      }
-      return this._store[key];
-    },
-
-    set: function(value) {
-      warning(
-        false,
-        'Don\'t set the %s property of the React element. Instead, ' +
-        'specify the correct value when initially creating the element.',
-        key
-      );
-      this._store[key] = value;
-    },
-
-  });
-}
-
-/**
- * This is updated to true if the membrane is successfully created.
- */
-var useMutationMembrane = false;
-
-/**
- * Warn for mutations.
- *
- * @internal
- * @param {object} prototype
- */
-function defineMutationMembrane(prototype) {
-  try {
-    var pseudoFrozenProperties = {
-      props: true,
-    };
-    for (var key in pseudoFrozenProperties) {
-      defineWarningProperty(prototype, key);
-    }
-    useMutationMembrane = true;
-  } catch (x) {
-    // IE will fail on defineProperty
-  }
-}
-
 /**
  * Base constructor for all React elements. This is only used to make this
  * work with a dynamic instanceof check. Nothing should live on this prototype.
@@ -100,11 +41,11 @@ var ReactElement = function(type, key, ref, owner, props) {
   this._owner = owner;
 
   if (__DEV__) {
-    // The validation flag and props are currently mutative. We put them on
+    // The validation flag is currently mutative. We put it on
     // an external backing store so that we can freeze the whole object.
     // This can be replaced with a WeakMap once they are implemented in
     // commonly used development environments.
-    this._store = {props: props, originalProps: assign({}, props)};
+    this._store = {};
 
     // To make comparing ReactElements easier for testing purposes, we make
     // the validation flag non-enumerable (where possible, which should
@@ -115,21 +56,15 @@ var ReactElement = function(type, key, ref, owner, props) {
         configurable: false,
         enumerable: false,
         writable: true,
+        value: false,
       });
     } catch (x) {
+      this._store.validated = false;
     }
-    this._store.validated = false;
-
-    // We're not allowed to set props directly on the object so we early
-    // return and rely on the prototype membrane to forward to the backing
-    // store.
-    if (useMutationMembrane) {
-      Object.freeze(this);
-      return;
-    }
+    this.props = props;
+    Object.freeze(this.props);
+    Object.freeze(this);
   }
-
-  this.props = props;
 };
 
 // We intentionally don't expose the function on the constructor property.
@@ -138,10 +73,6 @@ ReactElement.prototype = {
   _isReactElement: true,
 };
 
-if (__DEV__) {
-  defineMutationMembrane(ReactElement.prototype);
-}
-
 ReactElement.createElement = function(type, config, children) {
   var propName;
 
@@ -219,6 +150,7 @@ ReactElement.cloneAndReplaceProps = function(oldElement, newProps) {
     // If the key on the original is valid, then the clone is valid
     newElement._store.validated = oldElement._store.validated;
   }
+
   return newElement;
 };
 
diff --git a/src/isomorphic/classic/element/ReactElementValidator.js b/src/isomorphic/classic/element/ReactElementValidator.js
index a7067ec0457ff..d4c2df2a077df 100644
--- a/src/isomorphic/classic/element/ReactElementValidator.js
+++ b/src/isomorphic/classic/element/ReactElementValidator.js
@@ -286,90 +286,6 @@ function checkPropTypes(componentName, propTypes, props, location) {
   }
 }
 
-var warnedPropsMutations = {};
-
-/**
- * Warn about mutating props when setting `propName` on `element`.
- *
- * @param {string} propName The string key within props that was set
- * @param {ReactElement} element
- */
-function warnForPropsMutation(propName, element) {
-  var type = element.type;
-  var elementName = typeof type === 'string' ? type : type.displayName;
-  var ownerName = element._owner ?
-    element._owner.getPublicInstance().constructor.displayName : null;
-
-  var warningKey = propName + '|' + elementName + '|' + ownerName;
-  if (warnedPropsMutations.hasOwnProperty(warningKey)) {
-    return;
-  }
-  warnedPropsMutations[warningKey] = true;
-
-  var elementInfo = '';
-  if (elementName) {
-    elementInfo = ' <' + elementName + ' />';
-  }
-  var ownerInfo = '';
-  if (ownerName) {
-    ownerInfo = ' The element was created by ' + ownerName + '.';
-  }
-
-  warning(
-    false,
-    'Don\'t set .props.%s of the React component%s. Instead, specify the ' +
-    'correct value when initially creating the element or use ' +
-    'React.cloneElement to make a new element with updated props.%s',
-    propName,
-    elementInfo,
-    ownerInfo
-  );
-}
-
-// Inline Object.is polyfill
-function is(a, b) {
-  if (a !== a) {
-    // NaN
-    return b !== b;
-  }
-  if (a === 0 && b === 0) {
-    // +-0
-    return 1 / a === 1 / b;
-  }
-  return a === b;
-}
-
-/**
- * Given an element, check if its props have been mutated since element
- * creation (or the last call to this function). In particular, check if any
- * new props have been added, which we can't directly catch by defining warning
- * properties on the props object.
- *
- * @param {ReactElement} element
- */
-function checkAndWarnForMutatedProps(element) {
-  if (!element._store) {
-    // Element was created using `new ReactElement` directly or with
-    // `ReactElement.createElement`; skip mutation checking
-    return;
-  }
-
-  var originalProps = element._store.originalProps;
-  var props = element.props;
-
-  for (var propName in props) {
-    if (props.hasOwnProperty(propName)) {
-      if (!originalProps.hasOwnProperty(propName) ||
-          !is(originalProps[propName], props[propName])) {
-        warnForPropsMutation(propName, element);
-
-        // Copy over the new value so that the two props objects match again
-        originalProps[propName] = props[propName];
-      }
-    }
-  }
-}
-
 /**
  * Given an element, validate that its props follow the propTypes definition,
  * provided by the type.
@@ -409,8 +325,6 @@ function validatePropTypes(element) {
 
 var ReactElementValidator = {
 
-  checkAndWarnForMutatedProps: checkAndWarnForMutatedProps,
-
   createElement: function(type, props, children) {
     // We warn in this case but don't throw. We expect the element creation to
     // succeed and there will likely be errors in render.
diff --git a/src/isomorphic/classic/element/__tests__/ReactElement-test.js b/src/isomorphic/classic/element/__tests__/ReactElement-test.js
index 0cb9f82a84d78..1e715e1f45579 100644
--- a/src/isomorphic/classic/element/__tests__/ReactElement-test.js
+++ b/src/isomorphic/classic/element/__tests__/ReactElement-test.js
@@ -37,7 +37,9 @@ describe('ReactElement', function() {
     expect(element.type).toBe(ComponentClass);
     expect(element.key).toBe(null);
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({});
+    var expectation = {};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('allows a string to be passed as the type', function() {
@@ -45,7 +47,9 @@ describe('ReactElement', function() {
     expect(element.type).toBe('div');
     expect(element.key).toBe(null);
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({});
+    var expectation = {};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('returns an immutable element', function() {
@@ -70,7 +74,9 @@ describe('ReactElement', function() {
     expect(element.type).toBe(ComponentClass);
     expect(element.key).toBe('12');
     expect(element.ref).toBe('34');
-    expect(element.props).toEqual({foo:'56'});
+    var expectation = {foo:'56'};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('coerces the key to a string', function() {
@@ -81,7 +87,9 @@ describe('ReactElement', function() {
     expect(element.type).toBe(ComponentClass);
     expect(element.key).toBe('12');
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({foo:'56'});
+    var expectation = {foo:'56'};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('preserves the owner on the element', function() {
@@ -243,84 +251,42 @@ describe('ReactElement', function() {
     expect(inst2.props.prop).toBe(null);
   });
 
-  it('warns when changing a prop after element creation', function() {
-    spyOn(console, 'error');
+  it('throws when changing a prop (in dev) after element creation', function() {
     var Outer = React.createClass({
       render: function() {
         var el = <div className="moo" />;
 
-        // This assignment warns but should still work for now.
-        el.props.className = 'quack';
-        expect(el.props.className).toBe('quack');
+        expect(function() {
+          el.props.className = 'quack';
+        }).toThrow();
+        expect(el.props.className).toBe('moo');
 
         return el;
       },
     });
     var outer = ReactTestUtils.renderIntoDocument(<Outer color="orange" />);
-    expect(React.findDOMNode(outer).className).toBe('quack');
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toContain(
-      'Don\'t set .props.className of the React component <div />.'
-    );
-    expect(console.error.argsForCall[0][0]).toContain(
-      'The element was created by Outer.'
-    );
-
-    console.error.reset();
-
-    // This also warns (just once per key/type pair)
-    outer.props.color = 'green';
-    outer.forceUpdate();
-    outer.props.color = 'purple';
-    outer.forceUpdate();
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toContain(
-      'Don\'t set .props.color of the React component <Outer />.'
-    );
+    expect(React.findDOMNode(outer).className).toBe('moo');
   });
 
-  it('warns when adding a prop after element creation', function() {
-    spyOn(console, 'error');
+  it('throws when adding a prop (in dev) after element creation', function() {
     var container = document.createElement('div');
     var Outer = React.createClass({
       getDefaultProps: () => ({sound: 'meow'}),
       render: function() {
         var el = <div>{this.props.sound}</div>;
 
-        // This assignment doesn't warn immediately (because we can't) but it
-        // warns upon mount.
-        el.props.className = 'quack';
-        expect(el.props.className).toBe('quack');
+        expect(function() {
+          el.props.className = 'quack';
+        }).toThrow();
+
+        expect(el.props.className).toBe(undefined);
 
         return el;
       },
     });
     var outer = React.render(<Outer />, container);
     expect(React.findDOMNode(outer).textContent).toBe('meow');
-    expect(React.findDOMNode(outer).className).toBe('quack');
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toContain(
-      'Don\'t set .props.className of the React component <div />.'
-    );
-    expect(console.error.argsForCall[0][0]).toContain(
-      'The element was created by Outer.'
-    );
-
-    console.error.reset();
-
-    var newOuterEl = <Outer />;
-    newOuterEl.props.sound = 'oink';
-    outer = React.render(newOuterEl, container);
-    expect(React.findDOMNode(outer).textContent).toBe('oink');
-    expect(React.findDOMNode(outer).className).toBe('quack');
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toContain(
-      'Don\'t set .props.sound of the React component <Outer />.'
-    );
+    expect(React.findDOMNode(outer).className).toBe('');
   });
 
   it('does not warn for NaN props', function() {
diff --git a/src/isomorphic/modern/class/__tests__/ReactES6Class-test.js b/src/isomorphic/modern/class/__tests__/ReactES6Class-test.js
index 9c1179f972b7f..e1c876bc71c7b 100644
--- a/src/isomorphic/modern/class/__tests__/ReactES6Class-test.js
+++ b/src/isomorphic/modern/class/__tests__/ReactES6Class-test.js
@@ -16,6 +16,10 @@ var React;
 describe('ReactES6Class', function() {
 
   var container;
+  var freeze = function(expectation) {
+    Object.freeze(expectation);
+    return expectation;
+  };
   var Inner;
   var attachedListener = null;
   var renderedName = null;
@@ -288,10 +292,10 @@ describe('ReactES6Class', function() {
     lifeCycles = []; // reset
     test(<Foo value="bar" />, 'SPAN', 'bar');
     expect(lifeCycles).toEqual([
-      'receive-props', {value: 'bar'},
-      'should-update', {value: 'bar'}, {},
-      'will-update', {value: 'bar'}, {},
-      'did-update', {value: 'foo'}, {},
+      'receive-props', freeze({value: 'bar'}),
+      'should-update', freeze({value: 'bar'}), {},
+      'will-update', freeze({value: 'bar'}), {},
+      'did-update', freeze({value: 'foo'}), {},
     ]);
     lifeCycles = []; // reset
     React.unmountComponentAtNode(container);
diff --git a/src/isomorphic/modern/element/__tests__/ReactJSXElement-test.js b/src/isomorphic/modern/element/__tests__/ReactJSXElement-test.js
index 06ec4fe9f91de..caf4e7f923615 100644
--- a/src/isomorphic/modern/element/__tests__/ReactJSXElement-test.js
+++ b/src/isomorphic/modern/element/__tests__/ReactJSXElement-test.js
@@ -34,7 +34,9 @@ describe('ReactJSXElement', function() {
     expect(element.type).toBe(Component);
     expect(element.key).toBe(null);
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({});
+    var expectation = {};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('allows a lower-case to be passed as the string type', function() {
@@ -42,7 +44,9 @@ describe('ReactJSXElement', function() {
     expect(element.type).toBe('div');
     expect(element.key).toBe(null);
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({});
+    var expectation = {};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('allows a string to be passed as the type', function() {
@@ -51,7 +55,9 @@ describe('ReactJSXElement', function() {
     expect(element.type).toBe('div');
     expect(element.key).toBe(null);
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({});
+    var expectation = {};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('returns an immutable element', function() {
@@ -72,7 +78,9 @@ describe('ReactJSXElement', function() {
     expect(element.type).toBe(Component);
     expect(element.key).toBe('12');
     expect(element.ref).toBe('34');
-    expect(element.props).toEqual({foo:'56'});
+    var expectation = {foo:'56'};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('coerces the key to a string', function() {
@@ -80,7 +88,9 @@ describe('ReactJSXElement', function() {
     expect(element.type).toBe(Component);
     expect(element.key).toBe('12');
     expect(element.ref).toBe(null);
-    expect(element.props).toEqual({foo:'56'});
+    var expectation = {foo:'56'};
+    Object.freeze(expectation);
+    expect(element.props).toEqual(expectation);
   });
 
   it('merges JSX children onto the children prop', function() {
diff --git a/src/renderers/dom/client/ReactMount.js b/src/renderers/dom/client/ReactMount.js
index c4045117be3de..d0a0fdd8886fb 100644
--- a/src/renderers/dom/client/ReactMount.js
+++ b/src/renderers/dom/client/ReactMount.js
@@ -15,7 +15,6 @@ var DOMProperty = require('DOMProperty');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 var ReactCurrentOwner = require('ReactCurrentOwner');
 var ReactElement = require('ReactElement');
-var ReactElementValidator = require('ReactElementValidator');
 var ReactEmptyComponent = require('ReactEmptyComponent');
 var ReactInstanceHandles = require('ReactInstanceHandles');
 var ReactInstanceMap = require('ReactInstanceMap');
@@ -375,10 +374,6 @@ var ReactMount = {
       nextElement,
       container,
       callback) {
-    if (__DEV__) {
-      ReactElementValidator.checkAndWarnForMutatedProps(nextElement);
-    }
-
     ReactMount.scrollMonitor(container, function() {
       ReactUpdateQueue.enqueueElementInternal(prevComponent, nextElement);
       if (callback) {
diff --git a/src/renderers/shared/reconciler/ReactCompositeComponent.js b/src/renderers/shared/reconciler/ReactCompositeComponent.js
index c95a58593d422..d87372c6110a6 100644
--- a/src/renderers/shared/reconciler/ReactCompositeComponent.js
+++ b/src/renderers/shared/reconciler/ReactCompositeComponent.js
@@ -14,7 +14,6 @@
 var ReactComponentEnvironment = require('ReactComponentEnvironment');
 var ReactCurrentOwner = require('ReactCurrentOwner');
 var ReactElement = require('ReactElement');
-var ReactElementValidator = require('ReactElementValidator');
 var ReactInstanceMap = require('ReactInstanceMap');
 var ReactLifeCycle = require('ReactLifeCycle');
 var ReactNativeComponent = require('ReactNativeComponent');
@@ -503,12 +502,6 @@ var ReactCompositeComponentMixin = {
     }
 
     if (this._pendingStateQueue !== null || this._pendingForceUpdate) {
-      if (__DEV__) {
-        ReactElementValidator.checkAndWarnForMutatedProps(
-          this._currentElement
-        );
-      }
-
       this.updateComponent(
         transaction,
         this._currentElement,
diff --git a/src/renderers/shared/reconciler/ReactReconciler.js b/src/renderers/shared/reconciler/ReactReconciler.js
index a3cefe71a895c..c4067d7d6742d 100644
--- a/src/renderers/shared/reconciler/ReactReconciler.js
+++ b/src/renderers/shared/reconciler/ReactReconciler.js
@@ -12,7 +12,6 @@
 'use strict';
 
 var ReactRef = require('ReactRef');
-var ReactElementValidator = require('ReactElementValidator');
 
 /**
  * Helper to call ReactRef.attachRefs with this composite component, split out
@@ -36,11 +35,6 @@ var ReactReconciler = {
    */
   mountComponent: function(internalInstance, rootID, transaction, context) {
     var markup = internalInstance.mountComponent(rootID, transaction, context);
-    if (__DEV__) {
-      ReactElementValidator.checkAndWarnForMutatedProps(
-        internalInstance._currentElement
-      );
-    }
     if (internalInstance._currentElement.ref != null) {
       transaction.getReactMountReady().enqueue(attachRefs, internalInstance);
     }
@@ -83,10 +77,6 @@ var ReactReconciler = {
       return;
     }
 
-    if (__DEV__) {
-      ReactElementValidator.checkAndWarnForMutatedProps(nextElement);
-    }
-
     var refsChanged = ReactRef.shouldUpdateRefs(
       prevElement,
       nextElement