diff --git a/scripts/setupVitest.ts b/scripts/setupVitest.ts
index 81a78d2985a..c555b0fa5e8 100644
--- a/scripts/setupVitest.ts
+++ b/scripts/setupVitest.ts
@@ -1,4 +1,4 @@
-import { vi } from 'vitest'
+import { vi, type SpyInstance } from 'vitest'
 
 expect.extend({
   toHaveBeenWarned(received: string) {
@@ -65,7 +65,7 @@ expect.extend({
   }
 })
 
-let warn
+let warn: SpyInstance
 const asserted: Set<string> = new Set()
 
 beforeEach(() => {
diff --git a/tsconfig.json b/tsconfig.json
index bbe12407bc1..e575f0c4c90 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -33,6 +33,7 @@
     "packages/runtime-dom/types/jsx.d.ts",
     "packages/*/__tests__",
     "packages/dts-test",
-    "packages/vue/jsx-runtime"
+    "packages/vue/jsx-runtime",
+    "scripts/setupVitest.ts"
   ]
 }