Uncaught TypeError: Cannot read property 'replace' of undefined (react-router)

"react-router": "^2.2.4",
"react": "^0.14.8",
ES6

Uncaught TypeError: Cannot read property 'push' of undefined
Uncaught TypeError: Cannot read property 'replace' of undefined
Uncaught TypeError: Cannot read property 'transitionTo' of undefined

this.context.router is undefined · Issue #975 · reactjs/react-router · GitHub

同じファイルのクラス定義の後に、

Login.contextTypes = {
    router: React.PropTypes.func.isRequired
};

を足したらエラーにならなくなった。でもwarningになる。

Warning: Failed Context Types: Invalid context `router` of type `object` supplied to `Login`, expected `function`. Check the render method of `RouterContext`.
Login.contextTypes = {
    router: React.PropTypes.object.isRequired
};

に変えたら、Warningもなくなったっぽい。