When creating an Element with a ref from inside of a constructor an error is thrown in production mode, but not in dev mode.

Here is a minimal sample:
https://jsfiddle.net/84v837e9/35/

An error, "Only a ReactOwner can have refs", should happen in dev and production modes.

This is happening in React 15.4
render() {
        return <div ref={1} />;
      }
    }
    const a = ReactTestUtils.renderIntoDocument(<A />);
    expect(a.refs[1].nodeName).toBe('DIV');
  });
});
describe('string refs between fiber and stack', () => {
  beforeEach(() => {
    jest.resetModules();
    React = require('react');
    ReactTestUtils = require('react-dom/test-utils');
  });
  it('attaches, detaches from fiber component with stack layer', () => {
    const ReactCurrentOwner = require('ReactCurrentOwner');
    const ReactDOMStack = require('ReactDOMStackEntry');
    const ReactDOMFiber = require('ReactDOMFiberEntry');
    const ReactInstanceMap = require('ReactInstanceMap');
    let layerMounted = false;
    class A extends React.Component {