--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -913,7 +913,8 @@ gistoptions(Datum reloptions, bool validate)
 {
        static const relopt_parse_elt tab[] = {
                {"fillfactor", RELOPT_TYPE_INT, offsetof(GiSTOptions, fillfactor)},
-               {"buffering", RELOPT_TYPE_ENUM, offsetof(GiSTOptions, buffering_mode)}
+               {"buffering", RELOPT_TYPE_TERNARY,
+               offsetof(GiSTOptions, buffering_mode)}
        };