diff --git a/km3buu/cmd.py b/km3buu/cmd.py
index 3dd6e291f2ebea3eee59602f25c4d4064dfcfafc..0e81b9d084a95ca6943f240b21ee9cff529d2b3b 100755
--- a/km3buu/cmd.py
+++ b/km3buu/cmd.py
@@ -65,7 +65,7 @@ ARGPARSE_GENERAL_PARAMS = [{
     "dest": "timesteps",
     "type": int,
     "help": "The number of timesteps performed by GiBUU",
-    "required": False
+    "required": False,
     "default": -1
 }, {
     "option_strings": ["--geometry", "-g"],