diff --git a/src/addons/__tests__/ReactFragment-test.js b/src/addons/__tests__/ReactFragment-test.js
index 6b789e016a..d53e6020de 100644
--- a/src/addons/__tests__/ReactFragment-test.js
+++ b/src/addons/__tests__/ReactFragment-test.js
@@ -49,13 +49,13 @@ describe('ReactFragment', function() {
       z: <span />
     };
     var element = <div>{[children]}</div>;
+    expect(console.error.calls.length).toBe(0);
+    var container = document.createElement('div');
+    React.render(element, container);
     expect(console.error.calls.length).toBe(1);
     expect(console.error.calls[0].args[0]).toContain(
       'Any use of a keyed object'
     );
-    var container = document.createElement('div');
-    React.render(element, container);
-    expect(console.error.calls.length).toBe(1);
   });
 
   it('should warn if accessing any property on a fragment', function() {
diff --git a/src/isomorphic/classic/element/ReactElement.js b/src/isomorphic/classic/element/ReactElement.js
index 88d7f36c3e..4760c6311d 100644
--- a/src/isomorphic/classic/element/ReactElement.js
+++ b/src/isomorphic/classic/element/ReactElement.js
@@ -80,21 +80,6 @@ function defineMutationMembrane(prototype) {
   }
 }
 
-function markChildArrayValidated(childArray) {
-  // To make comparing ReactElements easier for testing purposes, we make the
-  // validation flag non-enumerable (where possible, which should include every
-  // environment we run tests in), so the test framework ignores it.
-  try {
-    Object.defineProperty(childArray, '_reactChildKeysValidated', {
-      configurable: false,
-      enumerable: false,
-      writable: true
-    });
-  } catch (x) {
-  }
-  childArray._reactChildKeysValidated = true;
-}
-
 /**
  * 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.
@@ -121,6 +106,20 @@ var ReactElement = function(type, key, ref, owner, context, props) {
     // commonly used development environments.
     this._store = {props: props, originalProps: assign({}, props)};
 
+    // To make comparing ReactElements easier for testing purposes, we make
+    // the validation flag non-enumerable (where possible, which should
+    // include every environment we run tests in), so the test framework
+    // ignores it.
+    try {
+      Object.defineProperty(this._store, 'validated', {
+        configurable: false,
+        enumerable: false,
+        writable: true
+      });
+    } catch (x) {
+    }
+    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.
@@ -171,9 +170,6 @@ ReactElement.createElement = function(type, config, children) {
     props.children = children;
   } else if (childrenLength > 1) {
     var childArray = Array(childrenLength);
-    if (__DEV__) {
-      markChildArrayValidated(childArray);
-    }
     for (var i = 0; i < childrenLength; i++) {
       childArray[i] = arguments[i + 2];
     }
@@ -220,6 +216,11 @@ ReactElement.cloneAndReplaceProps = function(oldElement, newProps) {
     oldElement._context,
     newProps
   );
+
+  if (__DEV__) {
+    // If the key on the original is valid, then the clone is valid
+    newElement._store.validated = oldElement._store.validated;
+  }
   return newElement;
 };
 
@@ -261,9 +262,6 @@ ReactElement.cloneElement = function(element, config, children) {
     props.children = children;
   } else if (childrenLength > 1) {
     var childArray = Array(childrenLength);
-    if (__DEV__) {
-      markChildArrayValidated(childArray);
-    }
     for (var i = 0; i < childrenLength; i++) {
       childArray[i] = arguments[i + 2];
     }
diff --git a/src/isomorphic/classic/element/ReactElementValidator.js b/src/isomorphic/classic/element/ReactElementValidator.js
index 93d14798da..48b0f44d6d 100644
--- a/src/isomorphic/classic/element/ReactElementValidator.js
+++ b/src/isomorphic/classic/element/ReactElementValidator.js
@@ -90,19 +90,15 @@ function getCurrentOwnerDisplayName() {
  * @internal
  * @param {ReactElement} element Element that requires a key.
  * @param {*} parentType element's parent's type.
- * @param {boolean} deep false if top-level collection, true if nested
  */
-function validateExplicitKey(element, parentType, deep) {
-  if (element.key != null) {
+function validateExplicitKey(element, parentType) {
+  if (element._store.validated || element.key != null) {
     return;
   }
+  element._store.validated = true;
+
   warnAndMonitorForKeyUse(
-    // We vary the message for nested key warning to allow filtering them out
-    // since we didn't historically warn in this case.
-    deep ?
-      'Each child in a nested array or iterator should have ' +
-      'a unique "key" prop.' :
-      'Each child in an array or iterator should have a unique "key" prop.',
+    'Each child in an array or iterator should have a unique "key" prop.',
     element,
     parentType
   );
@@ -116,17 +112,13 @@ function validateExplicitKey(element, parentType, deep) {
  * @param {string} name Property name of the key.
  * @param {ReactElement} element Component that requires a key.
  * @param {*} parentType element's parent's type.
- * @param {boolean} deep false if top-level collection, true if nested
  */
-function validatePropertyKey(name, element, parentType, deep) {
+function validatePropertyKey(name, element, parentType) {
   if (!NUMERIC_PROPERTY_REGEX.test(name)) {
     return;
   }
   warnAndMonitorForKeyUse(
-    deep ?
-      'Nested child objects should have non-numeric keys ' +
-      'so ordering is preserved.' :
-      'Child objects should have non-numeric keys so ordering is preserved.',
+    'Child objects should have non-numeric keys so ordering is preserved.',
     element,
     parentType
   );
@@ -188,29 +180,18 @@ function warnAndMonitorForKeyUse(message, element, parentType) {
  * @internal
  * @param {ReactNode} node Statically passed child of any type.
  * @param {*} parentType node's parent's type.
- * @param {boolean} deep false if top-level collection, true if nested
  */
-function validateChildKeys(node, parentType, deep) {
+function validateChildKeys(node, parentType) {
   if (Array.isArray(node)) {
-    if (node._reactChildKeysValidated) {
-      // All child elements were passed in a valid location.
-      return;
-    }
     for (var i = 0; i < node.length; i++) {
       var child = node[i];
       if (ReactElement.isValidElement(child)) {
-        validateExplicitKey(child, parentType, deep);
-      } else {
-        // TODO: Warn on unkeyed arrays and suggest using createFragment
-        validateChildKeys(child, parentType, true);
+        validateExplicitKey(child, parentType);
       }
     }
-  } else if (
-      typeof node === 'string' || typeof node === 'number' ||
-      ReactElement.isValidElement(node)
-    ) {
+  } else if (ReactElement.isValidElement(node)) {
     // This element was passed in a valid location.
-    return;
+    node._store.validated = true;
   } else if (node) {
     var iteratorFn = getIteratorFn(node);
     // Entry iterators provide implicit keys.
@@ -220,9 +201,7 @@ function validateChildKeys(node, parentType, deep) {
         var step;
         while (!(step = iterator.next()).done) {
           if (ReactElement.isValidElement(step.value)) {
-            validateExplicitKey(step.value, parentType, deep);
-          } else {
-            validateChildKeys(step.value, parentType, true);
+            validateExplicitKey(step.value, parentType);
           }
         }
       }
@@ -230,8 +209,7 @@ function validateChildKeys(node, parentType, deep) {
       var fragment = ReactFragment.extractIfFragment(node);
       for (var key in fragment) {
         if (fragment.hasOwnProperty(key)) {
-          validatePropertyKey(key, fragment[key], parentType, deep);
-          validateChildKeys(fragment[key], parentType, true);
+          validatePropertyKey(key, fragment[key], parentType);
         }
       }
     }
@@ -437,7 +415,7 @@ var ReactElementValidator = {
     }
 
     for (var i = 2; i < arguments.length; i++) {
-      validateChildKeys(arguments[i], type, false);
+      validateChildKeys(arguments[i], type);
     }
 
     validatePropTypes(element);
@@ -485,7 +463,7 @@ var ReactElementValidator = {
   cloneElement: function(element, props, children) {
     var newElement = ReactElement.cloneElement.apply(this, arguments);
     for (var i = 2; i < arguments.length; i++) {
-      validateChildKeys(arguments[i], newElement.type, false);
+      validateChildKeys(arguments[i], newElement.type);
     }
     validatePropTypes(newElement);
     return newElement;
diff --git a/src/isomorphic/classic/element/__tests__/ReactElementValidator-test.js b/src/isomorphic/classic/element/__tests__/ReactElementValidator-test.js
index fab2a7d789..26dd2fcafa 100644
--- a/src/isomorphic/classic/element/__tests__/ReactElementValidator-test.js
+++ b/src/isomorphic/classic/element/__tests__/ReactElementValidator-test.js
@@ -120,56 +120,6 @@ describe('ReactElementValidator', function() {
     );
   });
 
-  it('warns for keys for nested arrays of elements', function() {
-    spyOn(console, 'error');
-
-    var divs = [
-      [
-        <div />,
-        <div />
-      ],
-      <div key="foo" />
-    ];
-    ReactTestUtils.renderIntoDocument(<div>{divs}</div>);
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toBe(
-      'Warning: Each child in a nested array or iterator should have a ' +
-      'unique "key" prop. Check the React.render call using <div>. See ' +
-      'https://fb.me/react-warning-keys for more information.'
-    );
-  });
-
-  it('warns for keys when reusing children', function() {
-    spyOn(console, 'error');
-
-    var f = <span />;
-    var g = <span />;
-
-    var children = [f, g];
-
-    ReactTestUtils.renderIntoDocument(
-      <div>
-        <div key="0">
-          {g}
-        </div>
-        <div key="1">
-          {f}
-        </div>
-        <div key="2">
-          {children}
-        </div>
-      </div>
-    );
-
-    expect(console.error.argsForCall.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toBe(
-      'Warning: Each child in an array or iterator should have a unique ' +
-      '"key" prop. Check the React.render call using <div>. See ' +
-      'https://fb.me/react-warning-keys for more information.'
-    );
-  });
-
   it('does not warn for keys when passing children down', function() {
     spyOn(console, 'error');