[FIREBIRD] Creare una tabella con campo autoincrementale

[dail]

mi crea la tabella mi crea il generatore....ma mi da errore la trigger
questo il codice:

CREATE TABLE prova(
id INTEGER NOT NULL,
testo VARCHAR(255),
PRIMARY KEY(id)
);

CREATE GENERATOR GEN_PK_prova;
COMMIT;

CREATE TRIGGER BI_prova FOR prova
ACTIVE BEFORE INSERT
AS
BEGIN
  IF(NEW.id IS NULL) THEN 
    NEW.ID = GEN_ID(GEN_PK_prova, 1);
END

errore:

Starting transaction...
Preparing query: CREATE TRIGGER BI_prova FOR prova
ACTIVE BEFORE INSERT
AS
BEGIN
  IF(NEW.id IS NULL) THEN 
    NEW.ID = GEN_ID(GEN_PK_prova, 1)
*** IBPP::SQLException ***
Context: Statement::Prepare( CREATE TRIGGER BI_prova FOR prova
ACTIVE BEFORE INSERT
AS
BEGIN
  IF(NEW.id IS NULL) THEN 
    NEW.ID = GEN_ID(GEN_PK_prova, 1) )
Message: isc_dsql_prepare failed

SQL Message : -104
Invalid token

Engine Code    : 335544569
Engine Message :
Dynamic SQL Error
SQL error code = -104
Unexpected end of command


Execute time: 00:00:00.