diff --git a/src/node/serve/serve.ts b/src/node/serve/serve.ts
index 7a44d225..b51e169f 100644
--- a/src/node/serve/serve.ts
+++ b/src/node/serve/serve.ts
@@ -8,7 +8,7 @@ export interface ServeOptions {
 }
 
 export async function serve(options: ServeOptions = {}) {
-  const port = options.port ?? 3000
+  const port = options.port !== undefined ? options.port : 3000
   const site = await resolveConfig(options.root)
 
   const app = new Koa()