This might be a reference to this one: https://github.com/facebook/react/issues/10212#issuecomment-346302374

The problem still exist.

So, trying to render with server side and got this error. I don't have this notation in my code but this might be a problem with dependencies.

```
TypeError: Cannot read property 'toLowerCase' of undefined
    at ReactDOMServerRenderer.renderDOM (/Users/lukasborawski/Dev/web-client/node_modules/react-dom/cjs/react-dom-server.node.development.js:2304:27)
...
```

```
"react": "^16.1.1",
"react-dom": "^16.2.0",
```

Thx for help.
expect(() => {
          ReactDOM.render(<nonstandard />, document.createElement('div'));
        }).toWarnDev('The tag <nonstandard> is unrecognized in this browser.');
        const e = await render(<nonstandard>Text</nonstandard>);
        expect(e.tagName).toBe('NONSTANDARD');
        expect(e.childNodes.length).toBe(1);
        expectNode(e.firstChild, TEXT_NODE_TYPE, 'Text');
      });
      itRenders('a custom element with text', async render => {
        const e = await render(<custom-element>Text</custom-element>);
        expect(e.tagName).toBe('CUSTOM-ELEMENT');
        expect(e.childNodes.length).toBe(1);
        expectNode(e.firstChild, TEXT_NODE_TYPE, 'Text');
      });
      itRenders('a leading blank child with a text sibling', async render => {
        const e = await render(<div>{''}foo</div>);
        if (render === serverRender || render === streamRender) {
          expect(e.childNodes.length).toBe(1);
          expectTextNode(e.childNodes[0], 'foo');
        } else {
          expect(e.childNodes.length).toBe(2);
          expectTextNode(e.childNodes[0], '');
          expectTextNode(e.childNodes[1], 'foo');
        }
      });
      itRenders('a trailing blank child with a text sibling', async render => {
        const e = await render(<div>foo{''}</div>);
        
        if (render === serverRender || render === streamRender) {
          expect(e.childNodes.length).toBe(1);