diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1e0ce1..eba276a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# 8.0.0 / 2020-09-21
+
+- **BREAKING:** Support postcss v8 ([#344](https://github.com/postcss/postcss-cli/issues/344), [#349](https://github.com/postcss/postcss-cli/pull/349))
+- **BREAKING:** postcss is now a `peerDependency`, you must install it seperately ([#344](https://github.com/postcss/postcss-cli/issues/344), [#349](https://github.com/postcss/postcss-cli/pull/349))
+- Upgrade dependencies ([#340](https://github.com/postcss/postcss-cli/pull/340))
+
 # 7.1.2 / 2020-08-31
 
 - Make `--version` machine-readable ([#334](https://github.com/postcss/postcss-cli/issues/334), [#335](https://github.com/postcss/postcss-cli/pull/335))
diff --git a/README.md b/README.md
index 50bade6..71db6e6 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@
 <h2 align="center">Install</h2>
 
 ```bash
-npm i -g|-D postcss-cli
+npm i -D postcss postcss-cli
 ```
 
 <h2 align="center">Usage</h2>
diff --git a/lib/depGraph.js b/lib/depGraph.js
index 783d76e..ace18be 100644
--- a/lib/depGraph.js
+++ b/lib/depGraph.js
@@ -1,6 +1,6 @@
 'use strict'
 const path = require('path')
-const DepGraph = require('dependency-graph').DepGraph
+const { DepGraph } = require('dependency-graph')
 
 const graph = new DepGraph()
 
diff --git a/package.json b/package.json
index 0588ea6..75a7200 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "postcss-cli",
-  "version": "7.1.2",
+  "version": "8.0.0",
   "description": "CLI for PostCSS",
   "main": "index.js",
   "engines": {
@@ -24,24 +24,27 @@
     "fs-extra": "^9.0.0",
     "get-stdin": "^8.0.0",
     "globby": "^11.0.0",
-    "postcss": "^7.0.0",
-    "postcss-load-config": "^2.0.0",
-    "postcss-reporter": "^6.0.0",
+    "postcss-load-config": "^2.1.1",
+    "postcss-reporter": "^7.0.0",
     "pretty-hrtime": "^1.0.3",
     "read-cache": "^1.0.0",
-    "yargs": "^15.0.2"
+    "yargs": "^16.0.0"
   },
   "devDependencies": {
     "ava": "^3.1.0",
     "coveralls": "^3.0.0",
-    "eslint": "^6.8.0",
-    "eslint-config-problems": "4.0.0",
+    "eslint": "^7.8.0",
+    "eslint-config-problems": "5.0.0",
     "nyc": "^15.0.0",
+    "postcss": "^8.0.4",
     "postcss-import": "^12.0.0",
-    "prettier": "~2.0.0",
-    "sugarss": "^2.0.0",
+    "prettier": "~2.1.0",
+    "sugarss": "^3.0.0",
     "uuid": "^8.0.0"
   },
+  "peerDependencies": {
+    "postcss": "^8.0.0"
+  },
   "files": [
     "bin",
     "index.js",
diff --git a/test/.eslintrc.yaml b/test/.eslintrc.yaml
deleted file mode 100644
index add5a78..0000000
--- a/test/.eslintrc.yaml
+++ /dev/null
@@ -1,2 +0,0 @@
-parserOptions:
-  sourceType: module
diff --git a/test/base.js b/test/base.js
index 1bef3e3..32eff27 100644
--- a/test/base.js
+++ b/test/base.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 const path = require('path')
 
diff --git a/test/cli.js b/test/cli.js
index d2e449c..0cdc7dc 100644
--- a/test/cli.js
+++ b/test/cli.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/config.js b/test/config.js
index 774e2f5..b8b3de5 100644
--- a/test/config.js
+++ b/test/config.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 const path = require('path')
 
diff --git a/test/dir.js b/test/dir.js
index 51c0b6e..ec4e60e 100644
--- a/test/dir.js
+++ b/test/dir.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 const path = require('path')
 
diff --git a/test/error.js b/test/error.js
index e53ce05..38b972b 100644
--- a/test/error.js
+++ b/test/error.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const tmp = require('./helpers/tmp.js')
@@ -27,19 +28,6 @@ test('--map && writing to stdout', (t) => {
   })
 })
 
-test.failing('invalid --config', (t) => {
-  return cli([
-    'test/fixtures/*.css',
-    '-c',
-    'test/postcss.config.js',
-    '-d',
-    tmp(),
-  ]).then(({ error, code }) => {
-    t.is(code, 1, 'expected non-zero error code')
-    t.regex(error.toString(), /ENOENT: no such file or directory/)
-  })
-})
-
 test('plugin not found', (t) => {
   return cli(['test/fixtures/a.css', '-u', 'postcss-plugin', '-o', tmp()]).then(
     ({ error, code }) => {
diff --git a/test/ext.js b/test/ext.js
index 3f6e883..7016782 100644
--- a/test/ext.js
+++ b/test/ext.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const fs = require('fs-extra')
diff --git a/test/fixtures/_bad-plugin.js b/test/fixtures/_bad-plugin.js
index 2911e95..7a4ffeb 100644
--- a/test/fixtures/_bad-plugin.js
+++ b/test/fixtures/_bad-plugin.js
@@ -1 +1,2 @@
+'use strict'
 throw new Error('This fails')
diff --git a/test/glob.js b/test/glob.js
index 574cebb..e60b75a 100644
--- a/test/glob.js
+++ b/test/glob.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 const path = require('path')
 
diff --git a/test/helpers/clean.js b/test/helpers/clean.js
index 526bedf..cabfc72 100644
--- a/test/helpers/clean.js
+++ b/test/helpers/clean.js
@@ -1,4 +1,4 @@
-'use strict' // eslint-disable-line
+'use strict'
 const fs = require('fs-extra')
 
 Promise.all([
diff --git a/test/helpers/cli.js b/test/helpers/cli.js
index 7512439..64b9154 100644
--- a/test/helpers/cli.js
+++ b/test/helpers/cli.js
@@ -1,3 +1,4 @@
+'use strict'
 const path = require('path')
 const { exec } = require('child_process')
 
diff --git a/test/helpers/env.js b/test/helpers/env.js
index 2fad200..b389370 100644
--- a/test/helpers/env.js
+++ b/test/helpers/env.js
@@ -1,3 +1,4 @@
+'use strict'
 const fs = require('fs-extra')
 const path = require('path')
 const globby = require('globby')
diff --git a/test/helpers/read.js b/test/helpers/read.js
index 3122ee1..88b6421 100644
--- a/test/helpers/read.js
+++ b/test/helpers/read.js
@@ -1,3 +1,4 @@
+'use strict'
 const { readFile } = require('fs-extra')
 
 module.exports = function (path) {
diff --git a/test/helpers/tmp.js b/test/helpers/tmp.js
index f084dea..a23fa35 100644
--- a/test/helpers/tmp.js
+++ b/test/helpers/tmp.js
@@ -1,3 +1,4 @@
+'use strict'
 const path = require('path')
 const { v4: uuid } = require('uuid')
 
diff --git a/test/map.js b/test/map.js
index ac64a78..04f90fd 100644
--- a/test/map.js
+++ b/test/map.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 const fs = require('fs-extra')
 
diff --git a/test/misc.js b/test/misc.js
index 29a736c..9240e32 100644
--- a/test/misc.js
+++ b/test/misc.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/parser.js b/test/parser.js
index 4c56abb..1ac9805 100644
--- a/test/parser.js
+++ b/test/parser.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/replace.js b/test/replace.js
index 5b48ad4..f2712a2 100644
--- a/test/replace.js
+++ b/test/replace.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const fs = require('fs-extra')
diff --git a/test/stdin.js b/test/stdin.js
index 867145c..8709a94 100644
--- a/test/stdin.js
+++ b/test/stdin.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const fs = require('fs-extra')
diff --git a/test/stdout.js b/test/stdout.js
index 9b26ad4..8bd5d7b 100644
--- a/test/stdout.js
+++ b/test/stdout.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const fs = require('fs-extra')
diff --git a/test/stringifier.js b/test/stringifier.js
index 4256c79..db3ef28 100644
--- a/test/stringifier.js
+++ b/test/stringifier.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/syntax.js b/test/syntax.js
index 4658d69..c4295f9 100644
--- a/test/syntax.js
+++ b/test/syntax.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/use.js b/test/use.js
index 07901f6..25400f6 100644
--- a/test/use.js
+++ b/test/use.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const cli = require('./helpers/cli.js')
diff --git a/test/watch.js b/test/watch.js
index 6012bf7..b5bce40 100644
--- a/test/watch.js
+++ b/test/watch.js
@@ -1,3 +1,4 @@
+'use strict'
 const test = require('ava')
 
 const fs = require('fs-extra')