diff --git a/src/commands/build.ts b/src/commands/build.ts
index dd668f0..1d2dfc1 100644
--- a/src/commands/build.ts
+++ b/src/commands/build.ts
@@ -54,7 +54,8 @@ export default defineCommand({
         {
           input: 'src/runtime/',
           outDir: `${outDir}/runtime`,
-          ext: 'mjs',
+          addRelativeDeclarationExtensions: true,
+          ext: 'js',
           esbuild: {
             jsxImportSource: 'vue',
             jsx: 'automatic',
diff --git a/test/__snapshots__/JsxComponent.mjs b/test/__snapshots__/JsxComponent.js
similarity index 100%
rename from test/__snapshots__/JsxComponent.mjs
rename to test/__snapshots__/JsxComponent.js
diff --git a/test/build.spec.ts b/test/build.spec.ts
index d3d332e..c690f5a 100644
--- a/test/build.spec.ts
+++ b/test/build.spec.ts
@@ -38,7 +38,7 @@ describe('module builder', () => {
     expect(runtime).toMatchInlineSnapshot(`
       [
         "plugin.d.ts",
-        "plugin.mjs",
+        "plugin.js",
       ]
     `)
   })
@@ -109,10 +109,10 @@ describe('module builder', () => {
 
   it('should handle JSX correctly', async () => {
     const [component, declaration] = await Promise.all([
-      readFile(join(distDir, 'runtime/components/JsxComponent.mjs'), 'utf-8'),
+      readFile(join(distDir, 'runtime/components/JsxComponent.js'), 'utf-8'),
       readFile(join(distDir, 'runtime/components/JsxComponent.d.ts'), 'utf-8'),
     ])
-    expect(component).toMatchFileSnapshot('__snapshots__/JsxComponent.mjs')
+    expect(component).toMatchFileSnapshot('__snapshots__/JsxComponent.js')
     expect(declaration).toMatchFileSnapshot('__snapshots__/JsxComponent.d.ts')
   })
 })