**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
'instead.' +
          ReactDebugCurrentFrame.getStackAddendum();
      }
      var childrenString = '' + children;
      invariant(
        false,
        'Objects are not valid as a React child (found: %s).%s',
        childrenString === '[object Object]'
          ? 'object with keys {' + Object.keys(children).join(', ') + '}'
          : childrenString,
        addendum,
      );
    }
  }
  return subtreeCount;
}
/**
 * Traverses children that are typically specified as `props.children`, but
 * might also be specified through attributes:
 *
 * - `traverseAllChildren(this.props.children, ...)`
 * - `traverseAllChildren(this.props.leftPanelChildren, ...)`
 *
 * The `traverseContext` is an optional argument that is passed through the
 * entire traversal. It can be used to store accumulations or anything else that
 * the callback might find relevant.
 *
 * @param {?*} children Children tree object.
 * @param {!function} callback To invoke upon traversing each child.
 * @param {?*} traverseContext Context for traversal.