Javascript code for travel approver not running correctly!

Hello

I’m running this onload to get the travel approver roles only in .js file

cur_frm.set_query("travel_approver", function() {
	return {
		filters: [["UserRole", "role", "=", "Travel Approver"]]
	};
});

the problem is, it give me all the users in the system
this was running in version 4 , but now in version 5 not working … Am I missing something ?

This is the .json field for the Travel Approver

  {
   "fieldname": "travel_approver", 
   "fieldtype": "Link", 
   "label": "Travel Approver", 
   "options": "User", 
   "permlevel": 0, 
   "precision": "", 
   "reqd": 1
  },