diff --git a/lib/serve.js b/lib/serve.js
index 4e33340..9a9a688 100644
--- a/lib/serve.js
+++ b/lib/serve.js
@@ -20,8 +20,13 @@ module.exports = async (file, flags, restarting) => {
   const module = flags.silent ? getModule(file) : log(getModule(file))
   const server = serve(module)
 
-  // `3000` is the default port
-  let port = ~~flags.port
+  const { isNaN } = Number
+  let port = Number(flags.port)
+  
+  if (isNaN(port) || (!isNaN(port) && (port < 1 || port >= 2 ** 16))) {
+    console.error(`Port option must be a number. Supplied: ${flags.port}`)
+    process.exit(1)
+  }
 
   // Check if the specified port is already in use (if none
   // is specified, the default one will be checked)