diff --git a/lightningd/invoice.c b/lightningd/invoice.c
index 6f4253a40..a0feaea20 100644
--- a/lightningd/invoice.c
+++ b/lightningd/invoice.c
@@ -359,7 +359,7 @@ static void json_invoice(struct command *cmd,
 static const struct json_command invoice_command = {
 	"invoice",
 	json_invoice,
-	"Create an invoice for {msatoshi} with {label} and {description} with optional {expiry} seconds (default 1 hour)"
+	"Create an invoice for {msatoshi} with {label} and {description} with optional {expiry} seconds (default 1 hour) and optional {preimage} (default autogenerated)"
 };
 AUTODATA(json_command, &invoice_command);