diff --git a/packages/vite/src/node/plugins/esbuild.ts b/packages/vite/src/node/plugins/esbuild.ts
index 9a95c1be816580..c88d9a4210433d 100644
--- a/packages/vite/src/node/plugins/esbuild.ts
+++ b/packages/vite/src/node/plugins/esbuild.ts
@@ -27,7 +27,7 @@ import { searchForWorkspaceRoot } from '..'
 const debug = createDebugger('vite:esbuild')
 
 const INJECT_HELPERS_IIFE_RE =
-  /^(.*)((?:const|var) [^\s]+=function\([^)]*?\){"use strict";)/s
+  /^(.*)((?:var) [^\s]+=function\([^)]*?\){"use strict";)/s
 const INJECT_HELPERS_UMD_RE =
   /^(.*)(\(function\([^)]*?\){.+amd.+function\([^)]*?\){"use strict";)/s
 
diff --git a/playground/lib/__tests__/lib.spec.ts b/playground/lib/__tests__/lib.spec.ts
index 9046097f7e8375..b8143de14fdb81 100644
--- a/playground/lib/__tests__/lib.spec.ts
+++ b/playground/lib/__tests__/lib.spec.ts
@@ -23,7 +23,7 @@ describe.runIf(isBuild)('build', () => {
     expect(await page.textContent('.iife')).toBe('It works')
     const code = readFile('dist/my-lib-custom-filename.iife.js')
     // esbuild helpers are injected inside of the IIFE wrapper
-    expect(code).toMatch(/^const MyLib=function\(\){"use strict";/)
+    expect(code).toMatch(/^var MyLib=function\(\){"use strict";/)
   })
 
   test('Library mode does not include `preload`', async () => {
diff --git a/playground/lib/index.dist.html b/playground/lib/index.dist.html
index 99f08c73396fea..fd96f56ce0d651 100644
--- a/playground/lib/index.dist.html
+++ b/playground/lib/index.dist.html
@@ -27,11 +27,11 @@
 
 <script src="./my-lib-custom-filename.umd.js"></script>
 <script>
-  MyLib('.umd')
+  window.MyLib('.umd')
   delete window.MyLib // so that it won't affect iife
 </script>
 
 <script src="./my-lib-custom-filename.iife.js"></script>
 <script>
-  MyLib('.iife')
+  window.MyLib('.iife')
 </script>