---
slug: "Environment-key-es2021-is-unknown"
title: "If \"Environment key 'es2021' is unknown\" Occurs in Nuxt+Typescript"
description: "Fix `zlib`-related errors when `pip install mysqlclient` (old MySQL-python) — `brew install zlib` and add the right `LDFLAGS`."
url: "https://www.ytyng.com/en/blog/Environment-key-es2021-is-unknown"
publish_date: "2021-03-07T02:45:35Z"
created: "2021-03-07T02:45:35Z"
updated: "2026-05-11T13:21:46.459Z"
categories: []
keywords: ""
featured_image_url: "https://media.ytyng.com/resize/20230812/859dcb6639824c90ade062016fc708db.png.webp?width=768"
has_video: false
has_music: false
video_urls: []
music_urls: []
lang: "en"
---

# If "Environment key 'es2021' is unknown" Occurs in Nuxt+Typescript

<p>When developing with Nuxt + TypeScript and updating dependencies,</p>
<p></p>
<pre>Error: .eslintrc.js &raquo; @nuxtjs/eslint-config-typescript &raquo; @nuxtjs/eslint-config &raquo; eslint-config-standard:<br /> Environment key "es2021" is unknown</pre>
<p>appears,</p>
<p>update eslint to version 7 or above.</p>
<p></p>
<p>package.json</p>
<pre><span>"devDependencies"</span>: {<br />...<br />  <span>"eslint"</span>: <span>"^7.19.0"</span>,</pre>
<p></p>
<pre>npm install --also=dev</pre>
<p></p>