Primary index not getting dropped

I am trying to drop the primary index called #primary2 using the following statement. Need help !
DROP #primary2 INDEX ON xyz USING GSI;

But I keep getting
“code”: 3000,
“msg”: “syntax error - at primary2”,
“query_from_user”: “DROP #primary2 INDEX ON xyz USING GSI”

If Index name is primary2

DROP INDEX xyz.primary2;

It worked. thanks much vsri