React 16 alpha allows returning array in render function but server renderer expects children to always be react elements ``` TypeError: Cannot read property 'toLowerCase' of undefined at ReactDOMServerRenderer.renderDOM ``` source ```javascript function renderDOM(element, context) { var tag = element.type.toLowerCase(); // element is array ``` Fiddle: https://jsfiddle.net/84v837e9/160/ **react@16.0.0-alpha.13**