diff --git a/whisper_streaming/cli.py b/whisper_streaming/cli.py
index 754da19..8b3a428 100644
--- a/whisper_streaming/cli.py
+++ b/whisper_streaming/cli.py
@@ -75,7 +75,7 @@ def get_opts() -> argparse.Namespace:
     )
     parser.add_argument(
         "--num_block",
-        "-b",
+        "-n",
         type=int,
         default=20,
         help="Number of operation unit. Larger values can improve accuracy but consume more memory.",