diff --git a/webservice/update_mdc.py b/webservice/update_mdc.py
index cb1a9dfccdd468cbbe1ffd46893de714dbd65fee..f99417d211cf6b8db1b133ab4d0aaa6ef33bff2d 100644
--- a/webservice/update_mdc.py
+++ b/webservice/update_mdc.py
@@ -27,7 +27,8 @@ parser.add_argument('--runs', type=parse_int_range,
 parser.add_argument('--rid', type=int, help='Run id from MDC')
 parser.add_argument('--msg', type=str, help='Message string to MDC',
                     default='Error while job submission')
-parser.add_argument('--really', help="Actually make changes (otherwise dry-run)")
+parser.add_argument('--really', action='store_true',
+                    help="Actually make changes (otherwise dry-run)")
 args = parser.parse_args()
 
 if args.conf_file is not None: