Syntax check error- Found: 's' Expecting: string -or- XMLNAMESPACES when compiling (4307259)

Compiling the following procedure using F9 (execute statement) results in message

"Syntax check error- Found: 's' Expecting: string -or- XMLNAMESPACES"

and the procedure cannot be compiled. This syntax is correct for an 11gR2 database and compiles OK in sql*plus

create or replace procedure testt
as
s varchar2(2000);
begin
s:= '1,2,3';
for rec in (
SELECT TO_NUMBER(xt.column_value) lock_id
FROM XMLTABLE(s) xt
)
loop
dbms_output.put_line(rec.lock_id);
end loop;
end;
/