diff --git a/src/main.rs b/src/main.rs
index 14eefe0..53d362a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,7 +17,7 @@ struct Args {
     address: String,
     /// cluster host
     #[arg(short, long, num_args(0..))]
-    cluster: String,
+    cluster: Option<String>,
 }
 
 #[cfg(test)]