@intlify/unplugin-vue-i18n and vue-i18n $t syntax question

[yoyoys]

I've test @intlify/unplugin-vue-i18n with useI18n syntax and works fine:

<template>
  <div>{{ t('language') }}</div>
</template>
<script>
import { useI18n } from 'vue-i18n';

const { t } = useI18n();
</script>

<i18n>
{
  "en": {
    "language": "Languagex"
  }
}
</i18n>

But I got no effest with simple $t syntax

<template>
  <div>{{ $t('language') }}</div>
</template>

<i18n>
{
  "en": {
    "language": "Languagex"
  }
}
</i18n>

Is there any setting I've missed?