diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 65f4a4c83c42ec33d5ffe3f1d83d7b5465c0796d..b1b540f7f6cf90a8cec3816ffa4404449b9e5bb4 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -674,7 +674,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 		{ OPTION_CALLBACK, 'g', "reflog", &reflog_base, N_("<n>[,<base>]"),
 			    N_("show <n> most recent ref-log entries starting at "
 			       "base"),
-			    PARSE_OPT_OPTARG,
+			    PARSE_OPT_OPTARG | PARSE_OPT_NONEG,
 			    parse_reflog_param },
 		OPT_END()
 	};