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 />;
      }
      componentDidMount() {
        
        ReactCurrentOwner.current = ReactInstanceMap.get(this);
        const span = <span ref="span" />;
        ReactCurrentOwner.current = null;
        ReactDOMFiber.unstable_renderSubtreeIntoContainer(
          this,
          span,
          (this._container = document.createElement('div')),
          () => {
            expect(this.refs.span.nodeName).toBe('SPAN');
            layerMounted = true;
          },
        );
      }
      componentWillUnmount() {
        ReactDOMFiber.unmountComponentAtNode(this._container);