diff --git a/scripts/fiber/tests-failing.txt b/scripts/fiber/tests-failing.txt
index 77059f7db5..d816054f91 100644
--- a/scripts/fiber/tests-failing.txt
+++ b/scripts/fiber/tests-failing.txt
@@ -108,10 +108,6 @@ src/renderers/dom/stack/client/__tests__/ReactRenderDocument-test.js
 * should throw on full document render w/ no markup
 * supports findDOMNode on full-page components
 
-src/renderers/dom/stack/client/__tests__/findDOMNode-test.js
-* findDOMNode should reject random objects
-* findDOMNode should reject unmounted objects with render func
-
 src/renderers/dom/stack/server/__tests__/ReactServerRendering-test.js
 * should generate simple markup
 * should generate simple markup for self-closing tags
diff --git a/scripts/fiber/tests-passing.txt b/scripts/fiber/tests-passing.txt
index 1ceb9e0be3..069436ff51 100644
--- a/scripts/fiber/tests-passing.txt
+++ b/scripts/fiber/tests-passing.txt
@@ -908,6 +908,8 @@ src/renderers/dom/stack/client/__tests__/ReactMountDestruction-test.js
 src/renderers/dom/stack/client/__tests__/findDOMNode-test.js
 * findDOMNode should return null if passed null
 * findDOMNode should find dom element
+* findDOMNode should reject random objects
+* findDOMNode should reject unmounted objects with render func
 * findDOMNode should not throw an error when called within a component that is not mounted
 
 src/renderers/dom/stack/server/__tests__/ReactServerRendering-test.js
diff --git a/src/renderers/dom/fiber/ReactDOMFiber.js b/src/renderers/dom/fiber/ReactDOMFiber.js
index 1e1516aeec..91f25fe46a 100644
--- a/src/renderers/dom/fiber/ReactDOMFiber.js
+++ b/src/renderers/dom/fiber/ReactDOMFiber.js
@@ -12,6 +12,7 @@
 
 'use strict';
 
+import type { Fiber } from 'ReactFiber';
 import type { HostChildren } from 'ReactFiberReconciler';
 
 var ReactControlledComponent = require('ReactControlledComponent');
@@ -21,11 +22,7 @@ var ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');
 var ReactDOMFiberComponent = require('ReactDOMFiberComponent');
 var ReactDOMInjection = require('ReactDOMInjection');
 
-ReactDOMInjection.inject();
-ReactControlledComponent.injection.injectFiberControlledHostComponent(
-  ReactDOMFiberComponent
-);
-
+var findDOMNode = require('findDOMNode');
 var warning = require('warning');
 
 var {
@@ -35,6 +32,14 @@ var {
 } = ReactDOMFiberComponent;
 var { precacheFiberNode } = ReactDOMComponentTree;
 
+ReactDOMInjection.inject();
+ReactControlledComponent.injection.injectFiberControlledHostComponent(
+  ReactDOMFiberComponent
+);
+findDOMNode._injectFiber(function(fiber: Fiber) {
+  return DOMRenderer.findHostInstance(fiber);
+});
+
 type DOMContainerElement = Element & { _reactRootContainer: ?Object };
 
 type Container = Element;
@@ -167,17 +172,7 @@ var ReactDOM = {
     }
   },
 
-  findDOMNode(componentOrElement : Element | ?ReactComponent<any, any, any>) : null | Element | Text {
-    if (componentOrElement == null) {
-      return null;
-    }
-    // Unsound duck typing.
-    const component = (componentOrElement : any);
-    if (component.nodeType === 1) {
-      return component;
-    }
-    return DOMRenderer.findHostInstance(component);
-  },
+  findDOMNode: findDOMNode,
 
   unstable_batchedUpdates<A>(fn : () => A) : A {
     return DOMRenderer.batchedUpdates(fn);
diff --git a/src/renderers/dom/stack/client/findDOMNode.js b/src/renderers/dom/shared/findDOMNode.js
similarity index 58%
rename from src/renderers/dom/stack/client/findDOMNode.js
rename to src/renderers/dom/shared/findDOMNode.js
index 4445705b32..b4d1bf21be 100644
--- a/src/renderers/dom/stack/client/findDOMNode.js
+++ b/src/renderers/dom/shared/findDOMNode.js
@@ -7,59 +7,59 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule findDOMNode
+ * @flow
  */
 
-'use strict';
-
 var ReactCurrentOwner = require('ReactCurrentOwner');
-var ReactDOMComponentTree = require('ReactDOMComponentTree');
 var ReactInstanceMap = require('ReactInstanceMap');
 
-var getHostComponentFromComposite = require('getHostComponentFromComposite');
+var getComponentName = require('getComponentName');
 var invariant = require('invariant');
 var warning = require('warning');
 
-/**
- * Returns the DOM node rendered by this element.
- *
- * See https://facebook.github.io/react/docs/react-dom.html#finddomnode
- *
- * @param {ReactComponent|DOMElement} componentOrElement
- * @return {?DOMElement} The root node of this element.
- */
-function findDOMNode(componentOrElement) {
+let findFiber = function(arg) {
+  invariant(false, 'Missing injection for fiber findDOMNode');
+};
+let findStack = function(arg) {
+  invariant(false, 'Missing injection for stack findDOMNode');
+};
+
+const findDOMNode = function(componentOrElement : Element | ?ReactComponent<any, any, any>) : null | Element | Text {
   if (__DEV__) {
     var owner = ReactCurrentOwner.current;
-    if (owner !== null) {
+    if (owner !== null && '_warnedAboutRefsInRender' in owner) {
       warning(
-        owner._warnedAboutRefsInRender,
+        (owner: any)._warnedAboutRefsInRender,
         '%s is accessing findDOMNode inside its render(). ' +
         'render() should be a pure function of props and state. It should ' +
         'never access something that requires stale data from the previous ' +
         'render, such as refs. Move this logic to componentDidMount and ' +
         'componentDidUpdate instead.',
-        owner.getName() || 'A component'
+        getComponentName(owner) || 'A component'
       );
-      owner._warnedAboutRefsInRender = true;
+      (owner: any)._warnedAboutRefsInRender = true;
     }
   }
   if (componentOrElement == null) {
     return null;
   }
-  if (componentOrElement.nodeType === 1) {
-    return componentOrElement;
+  if ((componentOrElement: any).nodeType === 1) {
+    return (componentOrElement: any);
   }
 
   var inst = ReactInstanceMap.get(componentOrElement);
   if (inst) {
-    inst = getHostComponentFromComposite(inst);
-    return inst ? ReactDOMComponentTree.getNodeFromInstance(inst) : null;
+    if (typeof inst.tag === 'number') {
+      return findFiber(inst);
+    } else {
+      return findStack(inst);
+    }
   }
 
   if (typeof componentOrElement.render === 'function') {
     invariant(
       false,
-      'findDOMNode was called on an unmounted component.'
+      'Unable to find node on an unmounted component.'
     );
   } else {
     invariant(
@@ -68,6 +68,13 @@ function findDOMNode(componentOrElement) {
       Object.keys(componentOrElement)
     );
   }
-}
+};
+
+findDOMNode._injectFiber = function(fn) {
+  findFiber = fn;
+};
+findDOMNode._injectStack = function(fn) {
+  findStack = fn;
+};
 
 module.exports = findDOMNode;
diff --git a/src/renderers/dom/stack/client/ReactDOMStackInjection.js b/src/renderers/dom/stack/client/ReactDOMStackInjection.js
index 6bf56262ac..379628873c 100644
--- a/src/renderers/dom/stack/client/ReactDOMStackInjection.js
+++ b/src/renderers/dom/stack/client/ReactDOMStackInjection.js
@@ -15,6 +15,7 @@ var ReactComponentEnvironment = require('ReactComponentEnvironment');
 var ReactComponentBrowserEnvironment =
   require('ReactComponentBrowserEnvironment');
 var ReactDOMComponent = require('ReactDOMComponent');
+var ReactDOMComponentTree = require('ReactDOMComponentTree');
 var ReactDOMEmptyComponent = require('ReactDOMEmptyComponent');
 var ReactDOMTextComponent = require('ReactDOMTextComponent');
 var ReactDefaultBatchingStrategy = require('ReactDefaultBatchingStrategy');
@@ -24,6 +25,9 @@ var ReactHostComponent = require('ReactHostComponent');
 var ReactReconcileTransaction = require('ReactReconcileTransaction');
 var ReactUpdates = require('ReactUpdates');
 
+var findDOMNode = require('findDOMNode');
+var getHostComponentFromComposite = require('getHostComponentFromComposite');
+
 var alreadyInjected = false;
 
 function inject() {
@@ -61,6 +65,11 @@ function inject() {
   );
 
   ReactComponentEnvironment.injection.injectEnvironment(ReactComponentBrowserEnvironment);
+
+  findDOMNode._injectStack(function(inst) {
+    inst = getHostComponentFromComposite(inst);
+    return inst ? ReactDOMComponentTree.getNodeFromInstance(inst) : null;
+  });
 }
 
 module.exports = {
diff --git a/src/renderers/dom/stack/client/__tests__/findDOMNode-test.js b/src/renderers/dom/stack/client/__tests__/findDOMNode-test.js
index 05b76d4fba..ea1e72e58c 100644
--- a/src/renderers/dom/stack/client/__tests__/findDOMNode-test.js
+++ b/src/renderers/dom/stack/client/__tests__/findDOMNode-test.js
@@ -54,7 +54,7 @@ describe('findDOMNode', () => {
     ReactDOM.unmountComponentAtNode(container);
 
     expect(() => ReactDOM.findDOMNode(inst)).toThrowError(
-      'findDOMNode was called on an unmounted component.'
+      'Unable to find node on an unmounted component.'
     );
   });
 
diff --git a/src/renderers/noop/ReactNoop.js b/src/renderers/noop/ReactNoop.js
index 4ff3f5b61c..f6c91e60a7 100644
--- a/src/renderers/noop/ReactNoop.js
+++ b/src/renderers/noop/ReactNoop.js
@@ -24,6 +24,7 @@ import type { UpdateQueue } from 'ReactFiberUpdateQueue';
 import type { HostChildren } from 'ReactFiberReconciler';
 
 var ReactFiberReconciler = require('ReactFiberReconciler');
+var ReactInstanceMap = require('ReactInstanceMap');
 var {
   AnimationPriority,
 } = require('ReactPriorityLevel');
@@ -209,7 +210,8 @@ var ReactNoop = {
     if (component.tag === TERMINAL_TAG || component.tag === TEXT_TAG) {
       return component;
     }
-    return NoopRenderer.findHostInstance(component);
+    const inst = ReactInstanceMap.get(component);
+    return inst ? NoopRenderer.findHostInstance(inst) : null;
   },
 
   flushAnimationPri() {
diff --git a/src/renderers/shared/fiber/ReactFiberReconciler.js b/src/renderers/shared/fiber/ReactFiberReconciler.js
index 820e745149..2f780f096b 100644
--- a/src/renderers/shared/fiber/ReactFiberReconciler.js
+++ b/src/renderers/shared/fiber/ReactFiberReconciler.js
@@ -78,7 +78,7 @@ export type Reconciler<C, I, TI> = {
   getPublicRootInstance(container : OpaqueNode) : (ReactComponent<any, any, any> | TI | I | null),
 
   // Use for findDOMNode/findHostNode. Legacy API.
-  findHostInstance(component : ReactComponent<any, any, any>) : I | TI | null,
+  findHostInstance(component : Fiber) : I | TI | null,
 };
 
 module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) : Reconciler<C, I, TI> {
@@ -165,12 +165,12 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) :
       return containerFiber.child.stateNode;
     },
 
-    findHostInstance(component : ReactComponent<any, any, any>) : I | TI | null {
-      const fiber = findCurrentHostFiber(component);
-      if (!fiber) {
+    findHostInstance(fiber : Fiber) : I | TI | null {
+      const hostFiber = findCurrentHostFiber(fiber);
+      if (!hostFiber) {
         return null;
       }
-      return fiber.stateNode;
+      return hostFiber.stateNode;
     },
 
   };
diff --git a/src/renderers/shared/fiber/ReactFiberTreeReflection.js b/src/renderers/shared/fiber/ReactFiberTreeReflection.js
index 23485cd4ac..0f66e094bb 100644
--- a/src/renderers/shared/fiber/ReactFiberTreeReflection.js
+++ b/src/renderers/shared/fiber/ReactFiberTreeReflection.js
@@ -16,6 +16,8 @@ import type { Fiber } from 'ReactFiber';
 
 var ReactInstanceMap = require('ReactInstanceMap');
 
+var invariant = require('invariant');
+
 var {
   HostContainer,
   HostComponent,
@@ -27,18 +29,22 @@ var {
   Placement,
 } = require('ReactTypeOfSideEffect');
 
-function isFiberMounted(fiber : Fiber) : boolean {
+var MOUNTING = 1;
+var MOUNTED = 2;
+var UNMOUNTED = 3;
+
+function isFiberMounted(fiber : Fiber) : number {
   let node = fiber;
   if (!fiber.alternate) {
     // If there is no alternate, this might be a new tree that isn't inserted
     // yet. If it is, then it will have a pending insertion effect on it.
     if ((node.effectTag & Placement) !== NoEffect) {
-      return false;
+      return MOUNTING;
     }
     while (node.return) {
       node = node.return;
       if ((node.effectTag & Placement) !== NoEffect) {
-        return false;
+        return MOUNTING;
       }
     }
   } else {
@@ -49,10 +55,11 @@ function isFiberMounted(fiber : Fiber) : boolean {
   if (node.tag === HostContainer) {
     // TODO: Check if this was a nested HostContainer when used with
     // renderContainerIntoSubtree.
-    return true;
+    return MOUNTED;
   }
-  // If we didn't hit the root, that means that we're in an disconnected tree.
-  return false;
+  // If we didn't hit the root, that means that we're in an disconnected tree
+  // that has been unmounted.
+  return UNMOUNTED;
 }
 
 exports.isMounted = function(component : ReactComponent<any, any, any>) : boolean {
@@ -60,17 +67,18 @@ exports.isMounted = function(component : ReactComponent<any, any, any>) : boolea
   if (!fiber) {
     return false;
   }
-  return isFiberMounted(fiber);
+  return isFiberMounted(fiber) === MOUNTED;
 };
 
-exports.findCurrentHostFiber = function(component : ReactComponent<any, any, any>) : Fiber | null {
-  let parent = ReactInstanceMap.get(component);
-  if (!parent) {
-    return null;
-  }
-
-  if (!isFiberMounted(parent)) {
-    // First check if this node itself is mounted.
+exports.findCurrentHostFiber = function(parent : Fiber) : Fiber | null {
+  // First check if this node itself is mounted.
+  const state = isFiberMounted(parent, true);
+  if (state === UNMOUNTED) {
+    invariant(
+      false,
+      'Unable to find node on an unmounted component.'
+    );
+  } else if (state === MOUNTING) {
     return null;
   }