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

**What is the current behavior?**
I've started recieving this warning about my SVGs which is using [feGaussianBlur](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/feGaussianBlur): 
`Warning: Expected server HTML to contain a matching <feGaussianBlur> in <filter>.`

**What is the expected behavior?**
Should be no warnings because there are no difference.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Such behavior started right after updating to `React 16.0.0-rc.3` and never happened with `React 15.6.1`
if (typeof componentOrElement.render === 'function') {
      invariant(false, 'Unable to find node on an unmounted component.');
    } else {
      invariant(
        false,
        'Element appears to be neither ReactComponent nor DOMNode. Keys: %s',
        Object.keys(componentOrElement),
      );
    }
  },
  hydrate(element: React$Node, container: DOMContainer, callback: ?Function) {
    
    return renderSubtreeIntoContainer(null, element, container, true, callback);
  },
  render(
    element: React$Element<any>,
    container: DOMContainer,
    callback: ?Function,
  ) {
    return renderSubtreeIntoContainer(
      null,
      element,
      container,
      false,
      callback,
    );
  },
  unstable_renderSubtreeIntoContainer(
    parentComponent: React$Component<any, any>,
    element: React$Element<any>,