diff --git a/bloom/commands/generate.py b/bloom/commands/generate.py
index 166caaa8..6afee4fb 100644
--- a/bloom/commands/generate.py
+++ b/bloom/commands/generate.py
@@ -64,6 +64,7 @@ def create_subparsers(parser, generator_cmds):
         description='Call `bloom-generate {0} -h` for help on a each generate command.'.format(metavar),
         dest='generator_cmd'
     )
+    subparser.required = True
     for generator_cmd in generator_cmds:
         desc = load_generator_description(generator_cmd)
         cmd_parser = subparser.add_parser(desc['title'], description=desc['description'])