diff --git a/packages/plugin-legacy/README.md b/packages/plugin-legacy/README.md
index c2cfa4c45ef659..b73a4afb31be8b 100644
--- a/packages/plugin-legacy/README.md
+++ b/packages/plugin-legacy/README.md
@@ -156,7 +156,7 @@ The legacy plugin requires inline scripts for [Safari 10.1 `nomodule` fix](https
 
 - `sha256-MS6/3FCg4WjP9gwgaBGwLpRCY6fZBgwmhVCdrPrNf3E=`
 - `sha256-tQjf8gvb2ROOMapIxFvFAYBeUJ0v1HCbOcSmDNXGtDo=`
-- `sha256-8uUkKieevHiD3yYtzjkRvyDZWt+uZkBLuGEQWNiV3+c=`
+- `sha256-6gxDO54HJkJNWi7H6ipFpWWSkWSRpyuZYMGDyG6bcNE=`
 - `sha256-+5XkZFazzJo8n0iOP4ti/cLCMUudTf//Mzkb7xNPXIc=`
 
 <!--
diff --git a/packages/plugin-legacy/src/snippets.ts b/packages/plugin-legacy/src/snippets.ts
index 0b7838e09d1a9f..c0b49d7ae2b95d 100644
--- a/packages/plugin-legacy/src/snippets.ts
+++ b/packages/plugin-legacy/src/snippets.ts
@@ -7,8 +7,7 @@ export const legacyEntryId = 'vite-legacy-entry'
 export const systemJSInlineCode = `System.import(document.getElementById('${legacyEntryId}').getAttribute('data-src'))`
 
 const detectModernBrowserVarName = '__vite_is_modern_browser'
-export const detectModernBrowserDetector =
-  'import.meta.url;import("_").catch(()=>1);(async function* g(){})();'
+export const detectModernBrowserDetector = `import.meta.url;import("_").catch(()=>1);(async function*(){})().next()`
 export const detectModernBrowserCode = `${detectModernBrowserDetector}if(location.protocol!="file:"){window.${detectModernBrowserVarName}=true}`
 export const dynamicFallbackInlineCode = `!function(){if(window.${detectModernBrowserVarName})return;console.warn("vite: loading legacy chunks, syntax error above and the same error below should be ignored");var e=document.getElementById("${legacyPolyfillId}"),n=document.createElement("script");n.src=e.src,n.onload=function(){${systemJSInlineCode}},document.body.appendChild(n)}();`
 
diff --git a/playground/legacy/__tests__/legacy.spec.ts b/playground/legacy/__tests__/legacy.spec.ts
index 405c61f47e2700..b0cc061b289d6c 100644
--- a/playground/legacy/__tests__/legacy.spec.ts
+++ b/playground/legacy/__tests__/legacy.spec.ts
@@ -120,11 +120,13 @@ describe.runIf(isBuild)('build', () => {
     const terserPattern = /^(?:!function|System.register)/
 
     expect(findAssetFile(/chunk-async-legacy/)).toMatch(terserPattern)
-    expect(findAssetFile(/chunk-async\./)).not.toMatch(terserPattern)
+    expect(findAssetFile(/chunk-async(?!-legacy)/)).not.toMatch(terserPattern)
     expect(findAssetFile(/immutable-chunk-legacy/)).toMatch(terserPattern)
-    expect(findAssetFile(/immutable-chunk\./)).not.toMatch(terserPattern)
+    expect(findAssetFile(/immutable-chunk(?!-legacy)/)).not.toMatch(
+      terserPattern,
+    )
     expect(findAssetFile(/index-legacy/)).toMatch(terserPattern)
-    expect(findAssetFile(/index\./)).not.toMatch(terserPattern)
+    expect(findAssetFile(/index(?!-legacy)/)).not.toMatch(terserPattern)
     expect(findAssetFile(/polyfills-legacy/)).toMatch(terserPattern)
   })
 
@@ -149,4 +151,13 @@ describe.runIf(isBuild)('build', () => {
       ),
     ).toBeFalsy()
   })
+
+  test('should have only modern entry files guarded', async () => {
+    const guard = /(import\s*\()|(import.meta)|(async\s*function\*)/
+    expect(findAssetFile(/index(?!-legacy)/)).toMatch(guard)
+    expect(findAssetFile(/polyfills(?!-legacy)/)).toMatch(guard)
+
+    expect(findAssetFile(/chunk-async(?!-legacy)/)).not.toMatch(guard)
+    expect(findAssetFile(/index-legacy/)).not.toMatch(guard)
+  })
 })