pg12 - foreign key to partitions

Hey,
I was playing with the new features that were added to pg12 and I wanted to
ask something that looked weird for me.

Lets assume I have the following non partitions structure :

Product(id int PK,vendor int references Vendor(id),price int)
ProductPic(int picId PK,product int references product(id) )
Vendor(id int PK,name text)
.... more tables that has references to the Product(id).

Now, I successfully converted the current Product table into a hash
partition based on the vendor column. Now when I tried to recreate the fk
column ProductPic(product) - I'm getting the following error:
ERROR: there is no unique constraint matching given keys for referenced
table "Product"

during the conversion I had to create a PK on (id,vendor) because of the
partitioning. So in order to recreate all the references to the product
table I need to add to all those tables the vendor column also ? Isnt there
any other way to solve it ?