Creating mailmerge quote template

Hi all

I'm creating a custom mailmerge template for a quote. Now I have started from the standard "quote for customer" template. Modified it a little bit and then when I test it from that template it goes well. I save it and create a new mail merge template in CRM with template that I created. But then when I want to create a document using that template it keeps saying: Invalid merge field - This merge field is used in the main document, but it does not exist in the data source. It's referring to the field: Quote_Product_Product_Type

I'm really sure it's not being used in the template. Any idea?

Thx