diff --git a/src/renderers/__tests__/refs-test.js b/src/renderers/__tests__/refs-test.js
index 869dd3c78ce0e..6f16f2fd34e4c 100644
--- a/src/renderers/__tests__/refs-test.js
+++ b/src/renderers/__tests__/refs-test.js
@@ -489,12 +489,28 @@ describe('creating element with ref in constructor', () => {
     }
   }
 
-  var errorMessage =
+  var devErrorMessage =
     'addComponentAsRefTo(...): Only a ReactOwner can have refs. You might ' +
     "be adding a ref to a component that was not created inside a component's " +
     '`render` method, or you have multiple copies of React loaded ' +
     '(details: https://fb.me/react-refs-must-have-owner).';
 
+  var prodErrorMessage =
+    'Minified React error #119; visit ' +
+    'http://facebook.github.io/react/docs/error-decoder.html?invariant=119 for the full message ' +
+    'or use the non-minified dev environment for full errors and additional helpful warnings.';
+
+  var fiberDevErrorMessage =
+    'Element ref was specified as a string (p) but no owner was ' +
+    'set. You may have multiple copies of React loaded. ' +
+    '(details: https://fb.me/react-refs-must-have-owner).';
+
+  var fiberProdErrorMessage =
+    'Minified React error #149; visit ' +
+    'http://facebook.github.io/react/docs/error-decoder.html?invariant=149&args[]=p ' +
+    'for the full message or use the non-minified dev environment for full errors and additional ' +
+    'helpful warnings.';
+
   it('throws an error when __DEV__ = true', () => {
     ReactTestUtils = require('react-dom/test-utils');
 
@@ -504,7 +520,9 @@ describe('creating element with ref in constructor', () => {
     try {
       expect(function() {
         ReactTestUtils.renderIntoDocument(<RefTest />);
-      }).toThrowError(errorMessage);
+      }).toThrowError(
+        ReactDOMFeatureFlags.useFiber ? fiberDevErrorMessage : devErrorMessage,
+      );
     } finally {
       __DEV__ = originalDev;
     }
@@ -519,7 +537,11 @@ describe('creating element with ref in constructor', () => {
     try {
       expect(function() {
         ReactTestUtils.renderIntoDocument(<RefTest />);
-      }).toThrowError(errorMessage);
+      }).toThrowError(
+        ReactDOMFeatureFlags.useFiber
+          ? fiberProdErrorMessage
+          : prodErrorMessage,
+      );
     } finally {
       __DEV__ = originalDev;
     }
diff --git a/src/renderers/shared/fiber/ReactFiberCommitWork.js b/src/renderers/shared/fiber/ReactFiberCommitWork.js
index a5518140e3719..d6ed708926b45 100644
--- a/src/renderers/shared/fiber/ReactFiberCommitWork.js
+++ b/src/renderers/shared/fiber/ReactFiberCommitWork.js
@@ -562,7 +562,7 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
 
   function commitAttachRef(finishedWork: Fiber) {
     const ref = finishedWork.ref;
-    if (typeof ref === 'function') {
+    if (ref !== null) {
       const instance = finishedWork.stateNode;
       switch (finishedWork.tag) {
         case HostComponent:
@@ -571,14 +571,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
         default:
           ref(instance);
       }
-    } else {
-      invariant(
-        false,
-        'addComponentAsRefTo(...): Only a ReactOwner can have refs. You might ' +
-          "be adding a ref to a component that was not created inside a component's " +
-          '`render` method, or you have multiple copies of React loaded ' +
-          '(details: https://fb.me/react-refs-must-have-owner).',
-      );
     }
   }