diff --git a/pimgen.py b/pimgen.py
index 088590c..f7710c1 100755
--- a/pimgen.py
+++ b/pimgen.py
@@ -341,7 +341,7 @@
     parser.add_argument(
         'command', metavar='COMMAND', type=str,
         choices=valid_commands.keys(),
-        help='Command to run.')
+        help='%s.' % " | ".join(valid_commands.keys()))
 
     args = parser.parse_args()