diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c
index a730f6a1aa..92e9d0d69f 100644
--- a/builtin/checkout-index.c
+++ b/builtin/checkout-index.c
@@ -172,7 +172,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 			N_("write the content to temporary files")),
 		OPT_STRING(0, "prefix", &state.base_dir, N_("string"),
 			N_("when creating files, prepend <string>")),
-		{ OPTION_CALLBACK, 0, "stage", NULL, "1-3|all",
+		{ OPTION_CALLBACK, 0, "stage", NULL, "(1|2|3|all)",
 			N_("copy out the files from named stage"),
 			PARSE_OPT_NONEG, option_parse_stage },
 		OPT_END()