diff --git a/parse-options.h b/parse-options.h
index 706de9729f..0d1f738f8d 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -117,6 +117,7 @@ typedef int parse_opt_subcommand_fn(int argc, const char **argv,
  *   PARSE_OPT_OPTARG: says that the argument is optional (not for BOOLEANs)
  *   PARSE_OPT_NOARG: says that this option does not take an argument
  *   PARSE_OPT_NONEG: says that this option cannot be negated
+ *                   (i.e. rejects "--no-<option>")
  *   PARSE_OPT_HIDDEN: this option is skipped in the default usage, and
  *                     shown only in the full usage.
  *   PARSE_OPT_LASTARG_DEFAULT: says that this option will take the default