diff --git a/src/soupjobs/run.py b/src/soupjobs/run.py
index 855e917..b9982d1 100644
--- a/src/soupjobs/run.py
+++ b/src/soupjobs/run.py
@@ -49,7 +49,8 @@ if __name__ == '__main__':
     parser.add_argument(
         '-o', '--output-format',
         type=str,
-        help="Set to either 'yaml', 'json' or 'simple' format"
+        choices=['simple', 'yaml', 'json'],
+        help="Determines the format in which results are returned to stdout"
     )
     kwargs = vars(parser.parse_args())
     os.environ[CONFIG_FILE_ENV_VAR] = str(kwargs.pop('config_file'))