**Do you want to request a *feature* or report a *bug*?**
BUG

**What is the current behavior?**
App doesn't render in IE11 and below.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/reactjs/69z2wepo/).**
- Build React app with Webpack
- Launch IE11 or below (not an emulator)
- You will see a blank screen or half-compiled React app with the following error:
![24f8f6e8-afde-11e6-9a6f-a3cc6355f55c](https://cloud.githubusercontent.com/assets/1647596/20527736/7b9075a8-b097-11e6-8ccb-d205b1908f31.png)

**What is the expected behavior?**
- To render as it does in Chrome, Firefox, etc.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
We've temporarily shrink-wrapped our dependencies so that we can continue to serve our app. We're starting to believe that it's coming from a dependency that `react`, `apollo`  or `webpack` may be relying on...

Shrink-wrapped versions of our dependencies (left is the new one that's broken and the right one is the old one that continues to work across all browsers) https://www.diffchecker.com/SyaJUcsk
let mixedRef = element.ref;
  if (mixedRef !== null && typeof mixedRef !== 'function') {
    if (element._owner) {
      const owner: ?Fiber = (element._owner: any);
      let inst;
      if (owner) {
        const ownerFiber = ((owner: any): Fiber);
        invariant(
          ownerFiber.tag === ClassComponent,
          'Stateless function components cannot have refs.',
        );
        inst = ownerFiber.stateNode;
      }
      invariant(
        inst,
        'Missing owner for string ref %s. This error is likely caused by a ' +
          'bug in React. Please file an issue.',
        mixedRef,
      );
      const stringRef = '' + mixedRef;
      
      if (
        current !== null &&
        current.ref !== null &&
        current.ref._stringRef === stringRef