fb2.0.3 on fedora

SET SQL DIALECT 3;
CREATE DATABASE 'localhost:/opt/unb/db/unbsl.fdb'
PAGE_SIZE 8192
DEFAULT CHARACTER SET UTF8;

DECLARE EXTERNAL FUNCTION lower
CSTRING(255)
RETURNS CSTRING(255) FREE_IT
ENTRY_POINT 'IB_UDF_lower' MODULE_NAME 'ib_udf';

Statement failed, SQLCODE = -104
Dynamic SQL Error
-SQL error code = -104
-Token unknown - line 1, column 27
-lower
At line 454 in file unbsl.ddl.sql