diff --git a/package.json b/package.json
index 876a4a3..1bf5a61 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,7 @@
     "lint:fix": "pnpm run lint --fix",
     "build": "tsdown",
     "dev": "tsdown --watch",
-    "test": "node --test tests/index.test.js",
+    "test": "node --test tests/index.test.ts",
     "test:bun": "bun test tests/bun.test.ts",
     "typecheck": "tsgo --noEmit",
     "format": "prettier --cache --write .",
diff --git a/src/index.ts b/src/index.ts
index 3653c39..7c97254 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -12,6 +12,8 @@ export interface Options {
 
 const RE_NODE_MODULES = /[/\\]node_modules[/\\]/
 
+export const loaded: Set<string> = new Set<string>()
+
 let deregister: (() => void) | undefined
 export function init({ skipNodeModules }: Options = {}): () => void {
   if (process.versions.bun) {
@@ -42,6 +44,7 @@ export function init({ skipNodeModules }: Options = {}): () => void {
       const parentUUID = getParentUUID(context.parentURL)
       if (!noCache && !parentUUID) return resolved
 
+      loaded.add(resolved.url)
       resolved.url = appendUUID(resolved.url, parentUUID || crypto.randomUUID())
       return resolved
     },
@@ -54,6 +57,7 @@ export function init({ skipNodeModules }: Options = {}): () => void {
 
   return (deregister = () => {
     hooks.deregister()
+    loaded.clear()
     deregister = undefined
   })
 }
diff --git a/tests/index.test.js b/tests/index.test.ts
similarity index 93%
rename from tests/index.test.js
rename to tests/index.test.ts
index 4344319..a6da94f 100644
--- a/tests/index.test.js
+++ b/tests/index.test.ts
@@ -1,8 +1,6 @@
-// @ts-check
-
 import assert from 'node:assert'
 import { afterEach, test } from 'node:test'
-import { clearRequireCache, init, unregister } from '../dist/index.mjs'
+import { clearRequireCache, init, unregister, loaded } from '../dist/index.mjs'
 
 afterEach(() => {
   unregister()
@@ -13,6 +11,7 @@ const RE_NO_CACHE = /\?no-cache=[0-9a-f-]{36}$/
 test('import attributes', async () => {
   const deregister = init()
   const { uuid, url, cjs, requireESM, importCJS, dynamicImportCJS } =
+    // @ts-ignore missing types
     await import('./fixtures/mod.js', {
       with: { cache: 'no' },
     })
@@ -22,9 +21,11 @@ test('import attributes', async () => {
     requireESM: requireESM2,
     importCJS: importCJS2,
     dynamicImportCJS: dynamicImportCJS2,
+    // @ts-ignore missing types
   } = await import('./fixtures/mod.js', {
     with: { cache: 'no' },
   })
+  assert(loaded.size > 0)
   clearRequireCache()
   const {
     uuid: uuid3,
@@ -68,6 +69,7 @@ test('import attributes', async () => {
   deregister()
 
   await assert.rejects(
+    // @ts-ignore missing types
     () => import('./fixtures/mod.js', { with: { cache: 'no' } }),
   )
 })
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 6ead994..8352d2b 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -1,6 +1,7 @@
 import { defineConfig } from 'tsdown'
 
 export default defineConfig({
+  dts: true,
   exports: true,
   deps: {
     onlyBundle: [],