Title field disaparead from "add product" and "modify product" form

I found a bug when replacing title for title_field on products AND product_display at the same time.

The title_field is then unavailable in the modify form and add product form.

If i disable the title_field in the product display, then it come back available in the modify and add form for products.

Hopes it can help someone ;-)

Salutations!