Entity Framework: Mapping internal property from generic base type

Question

I've got rather complicated real-life scenario of EF Mapping, which seems to work only if I break incapsulation. Maybe someone would clear it out how to do it correctly, or we'll accept it is a bug.

I have 2 projects, let's call them Domain and Persistance. Domain contains POCO classes, and exposes it's internals to Persistance by the InternalsVisibleTo attribute.

Inside the Domain (the aim is to persist the SomeProduct):

pubic class Company { ... }
pubic class InsuranceCompany : Company { ... }

pubic class Product<TCompany> where TCompany : Company
{
    ...
    public CustomValueType SomeProp { ... 
      // get/set from/into SomePropInternal 
    }
    internal string SomePropInternal { get;set; } 
    // exposed as internal to be accessible from EF mappings
}

public class SomeProduct : Product<InsuranceCompany> 
{
    ...
    public AnotherCustomValueType AnotherSomeProp { ... 
      // get/set from/into AnotherSomePropInternal 
    }
    internal string AnotherSomePropInternal { get;set; } 
    // exposed as internal to be accessible from EF mappings
}

I need to end with one table SomeProduct with all the fields. So, in the Persistance we have:

Inside the Persistance:

Base configuration type for all Products:

public class ProductEntityTypeConfiguration<TProduct, TCompany> : EntityTypeConfiguration<TProduct> 
    where TProduct : Product<TCompany> 
    where TCompany : Organization
{
    public ProductEntityTypeConfiguration() 
    {
        ...
        Property(_ => _.SomePropInternal)
            .IsRequired()
            .IsUnicode()
            .HasMaxLength(100);
    }
}

And for SomeProduct:

public class SomeProductMap : ProductEntityTypeConfiguration<SomeProduct, InsuranceCompany>
{
    public SomeProductMap()
    {
        ToTable("Business.SomeProduct");

        Property(_ => _.AnotherSomePropInternal)
            .IsRequired()
            .IsUnicode()
            .HasMaxLength(100);
    }
}

When I try to Add-Migration with these mappings, it says that SomePropInternal is not declared on the type SomeProduct.

If I change the internal string SomePropInternal to public string SomePropInternal migration gets created. It's the problem. I do not want to expose that must-be-private property.

For AnotherSomePropInternal everything works fine with internal.