diff --git a/packages/vite/src/node/plugins/css.ts b/packages/vite/src/node/plugins/css.ts
index 142a696662f5e3..585270f1e82423 100644
--- a/packages/vite/src/node/plugins/css.ts
+++ b/packages/vite/src/node/plugins/css.ts
@@ -553,8 +553,12 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
             ? normalizePath(path.relative(config.root, chunk.facadeModuleId))
             : chunk.name
 
+          const isEntry = chunk.isEntry && isPureCssChunk
           const lang = path.extname(cssAssetName).slice(1)
-          const cssFileName = ensureFileExt(cssAssetName, '.css')
+          const cssFileName = ensureFileExt(
+            isEntry ? chunk.name : cssAssetName,
+            '.css',
+          )
 
           chunkCSS = resolveAssetUrlsInCss(chunkCSS, cssAssetName)
           chunkCSS = await finalizeCss(chunkCSS, true, config)
@@ -566,7 +570,6 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
             source: chunkCSS,
           })
           const originalName = isPreProcessor(lang) ? cssAssetName : cssFileName
-          const isEntry = chunk.isEntry && isPureCssChunk
           generatedAssets
             .get(config)!
             .set(referenceId, { originalName, isEntry })
diff --git a/playground/backend-integration/__tests__/backend-integration.spec.ts b/playground/backend-integration/__tests__/backend-integration.spec.ts
index 8d067f0616775d..fa2a3d6070bb3d 100644
--- a/playground/backend-integration/__tests__/backend-integration.spec.ts
+++ b/playground/backend-integration/__tests__/backend-integration.spec.ts
@@ -37,7 +37,6 @@ describe.runIf(isBuild)('build', () => {
     const cssAssetEntry = manifest['global.css']
     const scssAssetEntry = manifest['nested/blue.scss']
     const imgAssetEntry = manifest['../images/logo.png']
-    const dirFooAssetEntry = manifest['../../dir/foo.css'] // '\\' should not be used even on windows
     expect(htmlEntry.css.length).toEqual(1)
     expect(htmlEntry.assets.length).toEqual(1)
     expect(cssAssetEntry?.file).not.toBeUndefined()
@@ -47,7 +46,9 @@ describe.runIf(isBuild)('build', () => {
     expect(scssAssetEntry?.isEntry).toEqual(true)
     expect(imgAssetEntry?.file).not.toBeUndefined()
     expect(imgAssetEntry?.isEntry).toBeUndefined()
-    expect(dirFooAssetEntry).not.toBeUndefined()
+    // use the entry name
+    expect(manifest['bar.css']).not.toBeUndefined()
+    expect(manifest['foo.css']).toBeUndefined()
   })
 })
 
diff --git a/playground/backend-integration/vite.config.js b/playground/backend-integration/vite.config.js
index 245f1324ded5ed..2c301d8e79b97e 100644
--- a/playground/backend-integration/vite.config.js
+++ b/playground/backend-integration/vite.config.js
@@ -19,7 +19,7 @@ function BackendIntegrationExample() {
         .map((filename) => [path.relative(root, filename), filename])
 
       entrypoints.push(['tailwindcss-colors', 'tailwindcss/colors.js'])
-      entrypoints.push(['foo.css', path.resolve(__dirname, './dir/foo.css')])
+      entrypoints.push(['bar.css', path.resolve(__dirname, './dir/foo.css')])
 
       return {
         build: {