Hibernate creates column without name when using “default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP”

i got the following entity:

@Entity
public class Person {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(columnDefinition="int(11)",nullable=false)
private int id;

@Column(columnDefinition="varchar(255)",nullable=false)
private String name;

@Column(columnDefinition="varchar(255)",nullable=false)
private String vorname;

@Column(columnDefinition="varchar(255)",nullable=false)
private String password;

@Column(columnDefinition="varchar(100)",nullable=false)
private String user;

@Column(columnDefinition="varchar(20)",nullable=false)
private String klasse;

@Temporal(TemporalType.TIMESTAMP)
@Column(name="timestamp",nullable = false,columnDefinition="default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP")
private Date timestamp = new Date();


public Person(){

}
@PreUpdate
public void updatePerson(){
    this.timestamp = new Date();
}


...getters
    ...setters

}

When invoking hibenate , i get an error when hibernate wants to create the table. it seems the errror occurs, beacause the column timestamp has no name:

ERROR: HHH000389: Unsuccessful: create table Person (id int(11) not null auto_increment, klasse varchar(20) not null, name varchar(255) not null, password varchar(255) not null, timestamp default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP not null, user varchar(100) not null, vorname varchar(255) not null, primary key (id)) type=MyISAM

Does anyone knows why hibernate does this ?