diff --git a/react/index.d.ts b/react/index.d.ts
index 92aa3a03fc..8d5edbab51 100644
--- a/react/index.d.ts
+++ b/react/index.d.ts
@@ -28,7 +28,7 @@ declare namespace React {
     interface ReactElement<P> {
         type: string | ComponentClass<P> | SFC<P>;
         props: P;
-        key?: Key;
+        key: Key | null;
     }
 
     interface SFCElement<P> extends ReactElement<P> {
@@ -74,7 +74,7 @@ declare namespace React {
     type ClassicFactory<P> = CFactory<P, ClassicComponent<P, ComponentState>>;
 
     interface DOMFactory<P extends DOMAttributes<T>, T extends Element> {
-        (props?: P & ClassAttributes<T>, ...children: ReactNode[]): DOMElement<P, T>;
+        (props?: P & ClassAttributes<T> | null, ...children: ReactNode[]): DOMElement<P, T>;
     }
 
     interface HTMLFactory<T extends HTMLElement> extends DOMFactory<HTMLAttributes<T>, T> {
@@ -93,7 +93,7 @@ declare namespace React {
 
     // Should be Array<ReactNode> but type aliases cannot be recursive
     type ReactFragment = {} | Array<ReactChild | any[] | boolean>;
-    type ReactNode = ReactChild | ReactFragment | boolean;
+    type ReactNode = ReactChild | ReactFragment | boolean | null | undefined;
 
     //
     // Top Level API
@@ -201,7 +201,7 @@ declare namespace React {
 
     type SFC<P> = StatelessComponent<P>;
     interface StatelessComponent<P> {
-        (props: P, context?: any): ReactElement<any> | null;
+        (props: P, context?: any): ReactElement<any>;
         propTypes?: ValidationMap<P>;
         contextTypes?: ValidationMap<any>;
         defaultProps?: P;
@@ -262,7 +262,7 @@ declare namespace React {
     }
 
     interface ComponentSpec<P, S> extends Mixin<P, S> {
-        render(): ReactElement<any>;
+        render(): ReactElement<any> | null;
 
         [propertyName: string]: any;
     }
@@ -2354,7 +2354,7 @@ declare namespace React {
     // ----------------------------------------------------------------------
 
     interface Validator<T> {
-        (object: T, key: string, componentName: string, ...rest: any[]): Error;
+        (object: T, key: string, componentName: string, ...rest: any[]): Error | null;
     }
 
     interface Requireable<T> extends Validator<T> {
diff --git a/react/react-tests.ts b/react/react-tests.ts
index 85bc4c0704..7cdecd9e86 100644
--- a/react/react-tests.ts
+++ b/react/react-tests.ts
@@ -41,7 +41,7 @@ var props: Props & React.ClassAttributes<{}> = {
     foo: 42
 };
 
-var container: Element;
+var container: Element = document.createElement("div");
 
 //
 // Top-Level API
@@ -49,11 +49,12 @@ var container: Element;
 
 var ClassicComponent: React.ClassicComponentClass<Props> =
     React.createClass<Props, State>({
+        displayName: "ClassicComponent",
         getDefaultProps() {
             return {
-                hello: undefined,
+                hello: "hello",
                 world: "peace",
-                foo: undefined
+                foo: 0,
             };
         },
         getInitialState() {
@@ -187,6 +188,10 @@ var domElement: React.ReactHTMLElement<HTMLDivElement> =
 // React.cloneElement
 var clonedElement: React.CElement<Props, ModernComponent> =
     React.cloneElement(element, { foo: 43 });
+
+React.cloneElement(element, {});
+React.cloneElement(element, {}, null);
+
 var clonedElement2: React.CElement<Props, ModernComponent> =
     // known problem: cloning with key or ref requires cast
     React.cloneElement(element, <React.ClassAttributes<ModernComponent>>{
@@ -240,18 +245,15 @@ domNode = ReactDOM.findDOMNode(domNode);
 
 var type: React.ComponentClass<Props> = element.type;
 var elementProps: Props = element.props;
-var key: React.Key = element.key;
-
-var t: React.ReactType;
-var name = typeof t === "string" ? t : t.displayName;
+var key = element.key;
 
 //
 // React Components
 // --------------------------------------------------------------------------
 
-var displayName: string = ClassicComponent.displayName;
-var defaultProps: Props = ClassicComponent.getDefaultProps();
-var propTypes: React.ValidationMap<Props> = ClassicComponent.propTypes;
+var displayName: string | undefined = ClassicComponent.displayName;
+var defaultProps: Props = ClassicComponent.getDefaultProps ? ClassicComponent.getDefaultProps() : <Props>{};
+var propTypes: React.ValidationMap<Props> | undefined = ClassicComponent.propTypes;
 
 //
 // Component API
@@ -282,7 +284,7 @@ class RefComponent extends React.Component<RCProps, {}> {
     }
 }
 
-var componentRef: RefComponent;
+var componentRef: RefComponent = new RefComponent();
 RefComponent.create({ ref: "componentRef" });
 // type of c should be inferred
 RefComponent.create({ ref: c => componentRef = c });
@@ -377,14 +379,14 @@ var PropTypesSpecification: React.ComponentSpec<any, any> = {
         }),
         requiredFunc: React.PropTypes.func.isRequired,
         requiredAny: React.PropTypes.any.isRequired,
-        customProp: function(props: any, propName: string, componentName: string) {
+        customProp: function(props: any, propName: string, componentName: string): Error | null {
             if (!/matchme/.test(props[propName])) {
                 return new Error("Validation failed!");
             }
             return null;
         },
         // https://facebook.github.io/react/warnings/dont-call-proptypes.html#fixing-the-false-positive-in-third-party-proptypes
-        percentage: (object: any, key: string, componentName: string, ...rest: any[]): Error => {
+        percentage: (object: any, key: string, componentName: string, ...rest: any[]): Error | null => {
             const error = React.PropTypes.number(object, key, componentName, ...rest);
             if (error) {
                 return error;
@@ -395,7 +397,7 @@ var PropTypesSpecification: React.ComponentSpec<any, any> = {
             return null;
         }
     },
-    render: (): React.ReactElement<any> => {
+    render: (): React.ReactElement<any> | null => {
         return null;
     }
 };
@@ -429,14 +431,14 @@ var ContextTypesSpecification: React.ComponentSpec<any, any> = {
         }),
         requiredFunc: React.PropTypes.func.isRequired,
         requiredAny: React.PropTypes.any.isRequired,
-        customProp: function(props: any, propName: string, componentName: string) {
+        customProp: function(props: any, propName: string, componentName: string): Error | null {
             if (!/matchme/.test(props[propName])) {
                 return new Error("Validation failed!");
             }
             return null;
         }
     },
-    render: (): React.ReactElement<any> => {
+    render: (): null => {
         return null;
     }
 };
@@ -499,7 +501,7 @@ createFragment({
 // --------------------------------------------------------------------------
 React.createFactory(CSSTransitionGroup)({
     component: React.createClass({
-        render: (): React.ReactElement<any> => null
+        render: (): null => null
     }),
     childFactory: (c) => c,
     transitionName: "transition",
@@ -605,16 +607,19 @@ var foundComponents: ModernComponent[] = TestUtils.scryRenderedComponentsWithTyp
 
 // ReactTestUtils custom type guards
 
-var emptyElement: React.ReactElement<{}>;
-if (TestUtils.isElementOfType(emptyElement, StatelessComponent)) {
-    emptyElement.props.foo;
+var emptyElement1: React.ReactElement<{}> = React.createElement(ModernComponent);
+if (TestUtils.isElementOfType(emptyElement1, StatelessComponent)) {
+    emptyElement1.props.foo;
+}
+var emptyElement2: React.ReactElement<{}> = React.createElement(StatelessComponent);
+if (TestUtils.isElementOfType(emptyElement2, StatelessComponent)) {
+    emptyElement2.props.foo;
 }
 
-var anyInstance: Element | React.Component<any, any>;
-if (TestUtils.isDOMComponent(anyInstance)) {
-    anyInstance.getAttribute("className");
-} else if (TestUtils.isCompositeComponent(anyInstance)) {
-    anyInstance.props;
+if (TestUtils.isDOMComponent(container)) {
+    container.getAttribute("className");
+} else if (TestUtils.isCompositeComponent(new ModernComponent())) {
+    new ModernComponent().props;
 }
 
 //
@@ -655,4 +660,4 @@ class ConstructorSpreadArgsPureComponent extends React.PureComponent<{}, {}> {
     constructor(...args: any[]) {
         super(...args);
     }
-}
\ No newline at end of file
+}
diff --git a/react/tsconfig.json b/react/tsconfig.json
index 55fd2537d4..d89fd3bdf7 100644
--- a/react/tsconfig.json
+++ b/react/tsconfig.json
@@ -8,7 +8,7 @@
         "module": "commonjs",
         "target": "es6",
         "noImplicitAny": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "baseUrl": "../",
         "typeRoots": [
             "../"