diff --git a/packages/plugin-legacy/src/index.ts b/packages/plugin-legacy/src/index.ts
index 9068935bed118b..308049324c5e1a 100644
--- a/packages/plugin-legacy/src/index.ts
+++ b/packages/plugin-legacy/src/index.ts
@@ -578,7 +578,7 @@ function viteLegacyPlugin(options: Options = {}): Plugin[] {
       if (isLegacyBundle(bundle, opts)) {
         // avoid emitting duplicate assets
         for (const name in bundle) {
-          if (bundle[name].type === 'asset') {
+          if (bundle[name].type === 'asset' && !/.+\.map$/.test(name)) {
             delete bundle[name]
           }
         }
diff --git a/playground/legacy/__tests__/legacy.spec.ts b/playground/legacy/__tests__/legacy.spec.ts
index 290f6b69ac1cf9..f4fe6cb6287c36 100644
--- a/playground/legacy/__tests__/legacy.spec.ts
+++ b/playground/legacy/__tests__/legacy.spec.ts
@@ -118,4 +118,15 @@ describe.runIf(isBuild)('build', () => {
     expect(findAssetFile(/polyfills-legacy/)).toMatch('"structuredClone"')
     expect(findAssetFile(/polyfills-\w{8}\./)).toMatch('"structuredClone"')
   })
+
+  test('should generate legacy sourcemap file', async () => {
+    expect(
+      listAssets().some((filename) => /index-legacy.+\.map$/.test(filename)),
+    ).toBeTruthy()
+    expect(
+      listAssets().some((filename) =>
+        /polyfills-legacy.+\.map$/.test(filename),
+      ),
+    ).toBeFalsy()
+  })
 })
diff --git a/playground/legacy/vite.config.js b/playground/legacy/vite.config.js
index 7adf0f784eeeb2..54de28b31949de 100644
--- a/playground/legacy/vite.config.js
+++ b/playground/legacy/vite.config.js
@@ -14,6 +14,7 @@ module.exports = {
   build: {
     cssCodeSplit: false,
     manifest: true,
+    sourcemap: true,
     rollupOptions: {
       input: {
         index: path.resolve(__dirname, 'index.html'),