diff --git a/aider/main.py b/aider/main.py
index d84573442c9..9ab8eb9b1fe 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -152,7 +152,7 @@ def main(argv=None, input=None, output=None, force_git_root=None):
         "--voice-language",
         metavar="VOICE_LANGUAGE",
         default="en",
-        help="Specify the language for voice (default: auto)",
+        help="Specify the language for voice using ISO 639-1 code (default: auto)",
     )
 
     ##########