扩展第三方组件？

Question

我正在尝试扩展第三方套餐：

<template>
<div>
    Some data
    <third-party-component></third-party-component>
</div>
</template>

<script>
import TPC from 'third-party-component';

export default {
    extends:TPC,
    props: {
        message: {
            type: Number,
            required: false
        }
    }
};
</script>

我得到了错误：

Uncaught TypeError: Cannot read property 'props' of undefined

我要去哪里错了？