diff --git a/whisper/transcribe.py b/whisper/transcribe.py
index 1c075a2..f46b868 100644
--- a/whisper/transcribe.py
+++ b/whisper/transcribe.py
@@ -504,14 +504,14 @@ def cli():
     def valid_model_name(name):
         if name in available_models() or os.path.exists(name):
             return name
-        raise ValueError(
+        raise argparse.ArgumentTypeError(
             f"model should be one of {available_models()} or path to a model checkpoint"
         )
 
     # fmt: off
     parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
     parser.add_argument("audio", nargs="+", type=str, help="audio file(s) to transcribe")
-    parser.add_argument("--model", default="small", type=valid_model_name, help="name of the Whisper model to use")
+    parser.add_argument("--model", default="small", type=valid_model_name, help=f"name of the Whisper model to use. Available models are: {', '.join(available_models())}. You can also specify a path to a model checkpoint.")
     parser.add_argument("--model_dir", type=str, default=None, help="the path to save model files; uses ~/.cache/whisper by default")
     parser.add_argument("--device", default="cuda" if torch.cuda.is_available() else "cpu", help="device to use for PyTorch inference")
     parser.add_argument("--output_dir", "-o", type=str, default=".", help="directory to save the outputs")