diff --git a/.prettierignore b/.prettierignore
index 0fc71ddd1..95541be45 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -11,3 +11,4 @@ playground/html/invalid.html
 playground/html/valid.html
 playground/external/public/slash@3.0.0.js
 playground/ssr-html/public/slash@3.0.0.js
+playground/worker/classic-worker.js
diff --git a/packages/vite/src/node/plugins/worker.ts b/packages/vite/src/node/plugins/worker.ts
index dcaed0473..2e614ec7e 100644
--- a/packages/vite/src/node/plugins/worker.ts
+++ b/packages/vite/src/node/plugins/worker.ts
@@ -265,7 +265,7 @@ export function webWorkerPlugin(config: ResolvedConfig): Plugin {
         }
         if (injectEnv) {
           const s = new MagicString(raw)
-          s.prepend(injectEnv)
+          s.prepend(injectEnv + ';\n')
           return {
             code: s.toString(),
             map: s.generateMap({ hires: 'boundary' }),
diff --git a/playground/worker/classic-worker.js b/playground/worker/classic-worker.js
index be6fa357e..d68c61c14 100644
--- a/playground/worker/classic-worker.js
+++ b/playground/worker/classic-worker.js
@@ -1,3 +1,5 @@
+(() => {})() // this is to test `importScripts` injection doesn't break the code
+
 let base = `/${self.location.pathname.split('/')[1]}`
 if (base.endsWith('.js') || base === `/worker-entries`) base = '' // for dev