Beta 5 throwing Failed prop type: Cannot read property 'isValidElementType' of undefined

[paradoxxxzero]

Since I upgraded to beta-5 I keep getting this error with webpack for some reason at this line: https://github.com/ReactTraining/react-router/blob/master/packages/react-router/modules/Route.js#L132

Upon further inspection, in the compiled file I have:

/* harmony import */ var react_is__WEBPACK_IMPORTED_MODULE_9__ = __webpack_require__(/*! react-is */ "./node_modules/react-is/index.js");
/* harmony import */ var react_is__WEBPACK_IMPORTED_MODULE_9___default = /*#__PURE__*/__webpack_require__.n(react_is__WEBPACK_IMPORTED_MODULE_9__);

// ...

if (props[propName] && !react_is__WEBPACK_IMPORTED_MODULE_9___default.a.isValidElementType(props[propName])) {

and react_is__WEBPACK_IMPORTED_MODULE_9___default.a is undefined but react_is__WEBPACK_IMPORTED_MODULE_9__.isValidElementType exists.

[mjackson]

Related discussion here: #6209 (comment)

[paradoxxxzero]

I confirm it now works with beta 6.
Thanks!