**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
var result = [];
  mapIntoWithKeyPrefixInternal(
    children,
    result,
    null,
    emptyFunction.thatReturnsArgument,
  );
  return result;
}
/**
 * Returns the first child in a collection of children and verifies that there
 * is only one child in the collection.
 *
 * See https://reactjs.org/docs/react-api.html#react.children.only
 *
 * The current implementation of this function assumes that a single child gets
 * passed without a wrapper, but the purpose of this helper function is to
 * abstract away the particular structure of children.
 *
 * @param {?object} children Child collection structure.
 * @return {ReactElement} The first and only `ReactElement` contained in the
 * structure.
 */
function onlyChild(children) {