Database model insert always returns 0

Hi guys,

My model always seems to return 0 after doing an insert, despite the insert succeeding. Looking at the CI code, I would have thought it returns the insert id. What am I doing wrong?

PHP Code:

class UserModel extends BaseModel {
  
    protected $table = 'myusertable';
    protected $primaryKey = 'uid';
      
    protected $allowedFields = ['uid', 'username'];

    protected $returnType = \App\Entities\User::class;
    protected $useTimestamps = true;
}

$data = [
 'uid' => '123',
 'username' => 'joe'
];
            
$insert_id = $model->insert($data);