Default items in list are duplicated after APP update

Hello,

   i'm adding default list items into the list by .xml under list instance.

eg.

<Data><Rows><Row><Field Name="Text">Accounting</Field></Row><Row><Field Name="Text">Accounts Payable</Field></Row>
        ....

After app is published to company app store catalog, installed to the team site and updated to new version, default items are duplicated.

How can this be fixed? eg. add only if they doesn't exists..

Thanks ;)