diff --git a/src/dummy.mjs b/src/dummy.mjs
new file mode 100644
index 0000000..a7764dc
--- /dev/null
+++ b/src/dummy.mjs
@@ -0,0 +1 @@
+// This is a dummy module for vite/rollup to resolve.
diff --git a/vite.config.ts b/vite.config.ts
index 604789d..e20f3fb 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -23,6 +23,9 @@ const version = `${pkg.version}-${shortCommit}`;
 
 // https://vitejs.dev/config/
 export default defineConfig({
+  worker: {
+    format: 'es',
+  },
   server: {
     fs: {
       // Note:
@@ -85,6 +88,7 @@ export default defineConfig({
   resolve: {
     alias: {
       '~': path.resolve(__dirname, 'src'),
+      module: path.resolve(__dirname, 'src', 'dummy.mjs'),
     },
   },
   build: {