SQL & PL/SQL

SELECT  DISTINCT(FC.FLFFCONFIGID) AS "idNum", FC.VENDOR AS "provider", 
                                NVL(VD.NAME,FC.NAME) AS "providorName", FC.FORMAT AS "format" 
                         FROM FLFFCONFIG FC, VENDORDETL VD WHERE FC.VENDOR = VD.VENDOR(+)
                         
for above query i am getting result,

while i am using in xml format like below, i am getting error;

SELECT XMLAGG(XMLELEMENT("listItem", XMLFOREST( DISTINCT(FC.FLFFCONFIGID) AS "idNum", FC.VENDOR AS "provider", 
                                NVL(VD.NAME,FC.NAME) AS "providorName", FC.FORMAT AS "format" ))).GETCLOBVAL()
                         FROM FLFFCONFIG FC, VENDORDETL VD WHERE FC.VENDOR = VD.VENDOR(+)
Error at Command Line:1 Column:48
Error report:
SQL Error: ORA-00936: missing expression
00936. 00000 -  "missing expression"
*Cause:    
*Action:

i think i am using distinct keyword.
error is in that , how to eliminate.