diff --git a/letsencrypt/scripts/main.py b/letsencrypt/scripts/main.py
index 5fc1a9bcb..1d7acda97 100755
--- a/letsencrypt/scripts/main.py
+++ b/letsencrypt/scripts/main.py
@@ -39,7 +39,7 @@ def main():
                         help="Revert configuration N number of checkpoints.")
     parser.add_argument("-B", "--keysize", dest="key_size", type=int,
                         default=CONFIG.RSA_KEY_SIZE, metavar="N",
-                        help="RSA key shall be sized N bits.")
+                        help="RSA key shall be sized N bits. [%d]" % CONFIG.RSA_KEY_SIZE)
     parser.add_argument("-k", "--revoke", dest="revoke", action="store_true",
                         help="Revoke a certificate.")
     parser.add_argument("-v", "--view-config-changes",