diff --git a/playground/legacy/__tests__/legacy.spec.ts b/playground/legacy/__tests__/legacy.spec.ts
index 290f6b69ac1cf9..ab273e224f7aed 100644
--- a/playground/legacy/__tests__/legacy.spec.ts
+++ b/playground/legacy/__tests__/legacy.spec.ts
@@ -88,6 +88,7 @@ describe.runIf(isBuild)('build', () => {
     expect(manifest['../../vite/legacy-polyfills-legacy'].src).toBe(
       '../../vite/legacy-polyfills-legacy',
     )
+    expect(manifest['custom-legacy.js'].file).toMatch(/chunk-X-legacy.\w{8}.js/)
     // modern polyfill
     expect(manifest['../../vite/legacy-polyfills']).toBeDefined()
     expect(manifest['../../vite/legacy-polyfills'].src).toBe(
diff --git a/playground/legacy/custom.js b/playground/legacy/custom.js
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/playground/legacy/main.js b/playground/legacy/main.js
index 91ba0b038104c4..bf1fa7e1120fc2 100644
--- a/playground/legacy/main.js
+++ b/playground/legacy/main.js
@@ -3,6 +3,7 @@ import viteSvgPath from './vite.svg'
 import MyWorker from './worker?worker'
 
 async function run() {
+  await import('./custom.js')
   const { fn } = await import('./async.js')
   fn()
 }
diff --git a/playground/legacy/vite.config.js b/playground/legacy/vite.config.js
index 7adf0f784eeeb2..d039799227dab1 100644
--- a/playground/legacy/vite.config.js
+++ b/playground/legacy/vite.config.js
@@ -23,6 +23,8 @@ module.exports = {
         chunkFileNames(chunkInfo) {
           if (chunkInfo.name === 'immutable-chunk') {
             return `assets/${chunkInfo.name}.js`
+          } else if (chunkInfo.name === 'custom') {
+            return 'assets/chunk-X.[hash].js'
           }
           return `assets/chunk-[name].[hash].js`
         },