create table with primary key and rowid field

Below is a create table statement that is generated by mySQL "show
create table" command:
CREATE TABLE `invoice_files` (
`file_name` varchar(128) default NULL,
`creation_date` datetime default '0000-00-00 00:00:00',
`last_update_date` datetime default '0000-00-00 00:00:00',
`page_count` int(11) default '0',
`invoice_count` int(11) default '0',
`sequence_number` int(11) default '0',
`max_sequence_number` int(11) default '0',
`type` varchar(5) default NULL,
`id` int(11) NOT NULL auto_increment,
`index_number` int(11) default '0',
`file_path` varchar(128) default NULL,
`server_id` int(11) default NULL,
`status` varchar(20) default NULL,
PRIMARY KEY (`id`)



I made some minor adjustments to make it more compliant with iseries.
One particular adjustment I did is the auto_increment keyword on the id
field. I removed that keyword and change the field type to rowid. When
I run this sql statement, I'm getting this error: Duplicate UNIQUE
constraint exists for table INVOICE_FILES in PDFSPLIT. Any idea why I'm
getting the error?

CREATE TABLE pdfsplit.invoice_files (
file_name varchar(128) default NULL,
creation_date timestamp default NULL,
last_update_date timestamp default NULL,
page_count int default 0,
invoice_count int default 0,
sequence_number int default 0,
max_sequence_number int default 0,
type varchar(5) default NULL,
id rowid not null,
index_number int default 0,
file_path varchar(128) default NULL,
server_id int default NULL,
status varchar(20) default NULL,
PRIMARY KEY (id))