diff --git a/packages/vite/src/node/plugins/esbuild.ts b/packages/vite/src/node/plugins/esbuild.ts
index 64a243f3e2493e..10484369f0d710 100644
--- a/packages/vite/src/node/plugins/esbuild.ts
+++ b/packages/vite/src/node/plugins/esbuild.ts
@@ -27,9 +27,9 @@ import { searchForWorkspaceRoot } from '..'
 const debug = createDebugger('vite:esbuild')
 
 const INJECT_HELPERS_IIFE_RE =
-  /(.*)((?:const|var) [^\s]+=function\([^)]*?\){"use strict";)(.*)/s
+  /^(.*)((?:const|var) [^\s]+=function\([^)]*?\){"use strict";)/s
 const INJECT_HELPERS_UMD_RE =
-  /(.*)(\(function\([^)]*?\){.+amd.+function\([^)]*?\){"use strict";)(.*)/s
+  /^(.*)(\(function\([^)]*?\){.+amd.+function\([^)]*?\){"use strict";)/s
 
 let server: ViteDevServer
 
@@ -273,7 +273,7 @@ export const buildEsbuildPlugin = (config: ResolvedConfig): Plugin => {
         if (injectHelpers) {
           res.code = res.code.replace(
             injectHelpers,
-            (_, helpers, header, rest) => header + helpers + rest
+            (_, helpers, header) => header + helpers
           )
         }
       }