diff --git a/src/index.ts b/src/index.ts
index cc2bd70..8a14784 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -22,7 +22,7 @@ program.command('run')
   .option('-p, --project <path>', 'path to project', process.cwd())
   .option('-a, --assets [path]', 'path relative to project for game assets. By default, it takes the assets definition from package.json.', 'assets')
   .option('--skipValidations', 'skip code validation', false)
-  .option('--port', 'port to run the server', '3000')
+  .option('--port [port]', 'port to run the server', '3000')
   .option('-g, --game', 'sets the program as a game', false)
   .option('-v, --verbose', 'print debugging information', false)
   .option('-d, --startDiagram', 'activate the dynamic diagram (only for games)', false)