diff --git a/packages/next/build/index.ts b/packages/next/build/index.ts
index 7f308632333f525..e55eafd73d1d13b 100644
--- a/packages/next/build/index.ts
+++ b/packages/next/build/index.ts
@@ -9,7 +9,7 @@ import { escapeStringRegexp } from '../shared/lib/escape-regexp'
 import findUp from 'next/dist/compiled/find-up'
 import { nanoid } from 'next/dist/compiled/nanoid/index.cjs'
 import { pathToRegexp } from 'next/dist/compiled/path-to-regexp'
-import path from 'path'
+import path, { join } from 'path'
 import formatWebpackMessages from '../client/dev/error-overlay/format-webpack-messages'
 import {
   STATIC_STATUS_PAGE_GET_INITIAL_PROPS_ERROR,
@@ -89,7 +89,6 @@ import {
   PageInfo,
   printCustomRoutes,
   printTreeView,
-  getCssFilePaths,
   getUnresolvedModuleFromError,
   copyTracedFiles,
   isReservedPage,
@@ -1364,10 +1363,22 @@ export default async function build(
     await writeBuildId(distDir, buildId)
 
     if (config.experimental.optimizeCss) {
-      const cssFilePaths = getCssFilePaths(buildManifest)
+      const globOrig =
+        require('next/dist/compiled/glob') as typeof import('next/dist/compiled/glob')
+
+      const cssFilePaths = await new Promise<string[]>((resolve, reject) => {
+        globOrig('**/*.css', { cwd: join(distDir, 'static') }, (err, files) => {
+          if (err) {
+            return reject(err)
+          }
+          resolve(files)
+        })
+      })
 
       requiredServerFiles.files.push(
-        ...cssFilePaths.map((filePath) => path.join(config.distDir, filePath))
+        ...cssFilePaths.map((filePath) =>
+          path.join(config.distDir, 'static', filePath)
+        )
       )
     }
 
diff --git a/packages/next/build/utils.ts b/packages/next/build/utils.ts
index e03721527c60634..6c4ea4a0d7089f5 100644
--- a/packages/next/build/utils.ts
+++ b/packages/next/build/utils.ts
@@ -1103,19 +1103,6 @@ export function detectConflictingPaths(
   }
 }
 
-export function getCssFilePaths(buildManifest: BuildManifest): string[] {
-  const cssFiles = new Set<string>()
-  Object.values(buildManifest.pages).forEach((files) => {
-    files.forEach((file) => {
-      if (file.endsWith('.css')) {
-        cssFiles.add(file)
-      }
-    })
-  })
-
-  return [...cssFiles]
-}
-
 export function getRawPageExtensions(pageExtensions: string[]): string[] {
   return pageExtensions.filter(
     (ext) => !ext.startsWith('client.') && !ext.startsWith('server.')
diff --git a/test/integration/critical-css/components/hello.js b/test/integration/critical-css/components/hello.js
new file mode 100644
index 000000000000000..018641433828b64
--- /dev/null
+++ b/test/integration/critical-css/components/hello.js
@@ -0,0 +1,5 @@
+import styles from './hello.module.css'
+
+export default function Hello() {
+  return <p className={styles.hello}>hello world</p>
+}
diff --git a/test/integration/critical-css/components/hello.module.css b/test/integration/critical-css/components/hello.module.css
new file mode 100644
index 000000000000000..aa586c7e9cff305
--- /dev/null
+++ b/test/integration/critical-css/components/hello.module.css
@@ -0,0 +1,3 @@
+.hello {
+  color: orange;
+}
diff --git a/test/integration/critical-css/pages/another.js b/test/integration/critical-css/pages/another.js
new file mode 100644
index 000000000000000..77c5991743842b7
--- /dev/null
+++ b/test/integration/critical-css/pages/another.js
@@ -0,0 +1,21 @@
+import styles from '../styles/index.module.css'
+import dynamic from 'next/dynamic'
+
+const Hello = dynamic(() => import('../components/hello'))
+
+export default function Home() {
+  return (
+    <div className={styles.hello}>
+      <p>Hello World</p>
+      <Hello />
+    </div>
+  )
+}
+
+export const getServerSideProps = () => {
+  return {
+    props: {
+      hello: 'world',
+    },
+  }
+}
diff --git a/test/integration/critical-css/pages/index.js b/test/integration/critical-css/pages/index.js
index c9d02372f123e5d..5b3e2c75f4ef89e 100644
--- a/test/integration/critical-css/pages/index.js
+++ b/test/integration/critical-css/pages/index.js
@@ -1,9 +1,11 @@
 import styles from '../styles/index.module.css'
+import Hello from '../components/hello'
 
 export default function Home() {
   return (
     <div className={styles.hello}>
       <p>Hello World</p>
+      <Hello />
     </div>
   )
 }
diff --git a/test/integration/critical-css/test/index.test.js b/test/integration/critical-css/test/index.test.js
index 502f4e839733133..2c1469866c4c43b 100644
--- a/test/integration/critical-css/test/index.test.js
+++ b/test/integration/critical-css/test/index.test.js
@@ -1,5 +1,6 @@
 /* eslint-env jest */
-
+import globOrigig from 'glob'
+import { promisify } from 'util'
 import { join } from 'path'
 import {
   killApp,
@@ -10,12 +11,29 @@ import {
 } from 'next-test-utils'
 import fs from 'fs-extra'
 
+const glob = promisify(globOrigig)
 const appDir = join(__dirname, '../')
 const nextConfig = join(appDir, 'next.config.js')
 let appPort
 let app
 
 function runTests() {
+  it('should have all CSS files in manifest', async () => {
+    const cssFiles = (
+      await glob('**/*.css', {
+        cwd: join(appDir, '.next/static'),
+      })
+    ).map((file) => join('.next/static', file))
+
+    const requiredServerFiles = await fs.readJSON(
+      join(appDir, '.next/required-server-files.json')
+    )
+
+    expect(
+      requiredServerFiles.files.filter((file) => file.endsWith('.css'))
+    ).toEqual(cssFiles)
+  })
+
   it('should inline critical CSS', async () => {
     const html = await renderViaHTTP(appPort, '/')
     expect(html).toMatch(
@@ -24,6 +42,14 @@ function runTests() {
     expect(html).toMatch(/body{font-family:SF Pro Text/)
   })
 
+  it('should inline critical CSS (dynamic)', async () => {
+    const html = await renderViaHTTP(appPort, '/another')
+    expect(html).toMatch(
+      /<link rel="stylesheet" href="\/_next\/static\/css\/.*\.css" .*>/
+    )
+    expect(html).toMatch(/body{font-family:SF Pro Text/)
+  })
+
   it('should not inline non-critical css', async () => {
     const html = await renderViaHTTP(appPort, '/')
     expect(html).not.toMatch(/.extra-style/)
@@ -45,22 +71,10 @@ describe('CSS optimization for SSR apps', () => {
     appPort = await findPort()
     app = await nextStart(appDir, appPort)
   })
-  afterAll(() => killApp(app))
-  runTests()
-})
-
-describe('CSS optimization for serverless apps', () => {
-  beforeAll(async () => {
-    await fs.writeFile(
-      nextConfig,
-      `module.exports = { target: 'serverless', experimental: {optimizeCss: true} }`,
-      'utf8'
-    )
-    await nextBuild(appDir)
-    appPort = await findPort()
-    app = await nextStart(appDir, appPort)
+  afterAll(async () => {
+    await killApp(app)
+    await fs.remove(nextConfig)
   })
-  afterAll(() => killApp(app))
   runTests()
 })