diff --git a/src/index.js b/src/index.js
index 7688e5b..e94d814 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,4 +1,4 @@
-import { act, cleanup } from './pure'
+import { act, cleanup } from './pure.js'
 
 // If we're running in a test runner that supports afterEach
 // then we'll automatically run cleanup afterEach test
@@ -12,4 +12,4 @@ if (typeof afterEach === 'function' && !process.env.STL_SKIP_AUTO_CLEANUP) {
   })
 }
 
-export * from './pure'
+export * from './pure.js'
diff --git a/src/test-setup.js b/src/test-setup.js
index fb76eb6..fe15b57 100644
--- a/src/test-setup.js
+++ b/src/test-setup.js
@@ -1,7 +1,7 @@
 import * as matchers from '@testing-library/jest-dom/dist/matchers'
 import { afterEach, expect } from 'vitest'
 
-import { act, cleanup } from './pure'
+import { act, cleanup } from './pure.js'
 
 expect.extend(matchers)