diff --git a/scripts/fiber/tests-failing.txt b/scripts/fiber/tests-failing.txt
index 46e114bb24..ae1b00f2df 100644
--- a/scripts/fiber/tests-failing.txt
+++ b/scripts/fiber/tests-failing.txt
@@ -26,7 +26,6 @@ src/renderers/dom/shared/__tests__/ReactDOMTextComponent-test.js
 * can reconcile text arbitrarily split into multiple nodes on some substitutions only
 
 src/renderers/dom/shared/__tests__/ReactMount-test.js
-* throws when given a non-node
 * throws when given a string
 * throws when given a factory
 * tracks root instances
diff --git a/scripts/fiber/tests-passing.txt b/scripts/fiber/tests-passing.txt
index 495ab14b83..ab34e72691 100644
--- a/scripts/fiber/tests-passing.txt
+++ b/scripts/fiber/tests-passing.txt
@@ -752,6 +752,7 @@ src/renderers/dom/shared/__tests__/ReactEventListener-test.js
 * should not fire duplicate events for a React DOM tree
 
 src/renderers/dom/shared/__tests__/ReactMount-test.js
+* throws when given a non-node
 * should render different components in same root
 * should unmount and remount if the key changes
 * should reuse markup if rendering to the same target twice
diff --git a/src/renderers/dom/fiber/ReactDOMFiber.js b/src/renderers/dom/fiber/ReactDOMFiber.js
index ed27da5ee9..79ad9a28de 100644
--- a/src/renderers/dom/fiber/ReactDOMFiber.js
+++ b/src/renderers/dom/fiber/ReactDOMFiber.js
@@ -352,6 +352,10 @@ var ReactDOM = {
   },
 
   unmountComponentAtNode(container : DOMContainerElement) {
+    invariant(
+      isValidContainer(container),
+      'unmountComponentAtNode(...): Target container is not a DOM element.'
+    );
     warnAboutUnstableUse();
     if (container._reactRootContainer) {
       // Unmount should not be batched.