When I try to create the following stored procedure I get sql error code = -206 Column unknown EMPID

SET TERM ! ;
CREATE OR ALTER PROCEDURE TEST (
  ATITLE DOM_VARCHARTINY,
  AFIRST_NAME DOM_VARCHARMEDIUM,
  AINITIALS DOM_VARCHARTINY,
  ASURNAME DOM_VARCHARMEDIUM,
  AEMAIL DOM_VARCHARLARGE,
  APHONE DOM_VARCHARTINY)
AS
begin
      INSERT INTO Employee (title, first_name, initials, surname,
                             email, phone_ext)
      VALUES(:ATitle, :AFirst_Name, :AInitials, :ASurname, :AEmail, :APhone)
      RETURNING :EMPID;     
end !
SET TERM ; !

The table does have a EMPID column defined and if I type the insert statement and execute it, it does work.