Can you remove Identity from a primary key with Entity Framework 6?

I created a table via entity framework code-first with a primary key set to auto increment, but now I want to remove that auto-incrementing from the column. I've tried doing that with both fluent API:

public class ProductTypeMap: EntityTypeConfiguration<ProductType>
{
    public ProductTypeMap()
    {
        // This is an enum effectively, so we need fixed IDs
        Property(x => x.ProductTypeId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
    }

}

And an annotation:

public class ProductType
{
    [Required, Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int ProductTypeId { get; set; }
    public string ProductTypeName { get; set; }

}

And in both cases they produce the same migration code:

public partial class removeproducttypeidentity : DbMigration
{
    public override void Up()
    {
        DropPrimaryKey("dbo.ProductTypes");
        AlterColumn("dbo.ProductTypes", "ProductTypeId", c => c.Int(nullable: false));
        AddPrimaryKey("dbo.ProductTypes", "ProductTypeId");
    }

    public override void Down()
    {
        DropPrimaryKey("dbo.ProductTypes");
        AlterColumn("dbo.ProductTypes", "ProductTypeId", c => c.Int(nullable: false, identity: true));
        AddPrimaryKey("dbo.ProductTypes", "ProductTypeId");
    }
}

However, when I run that migration on the database, the Identity Specification is not removed from the SQL Server 2008 database table?

I also tried explicitly turning off the Identity in the migration as follows, but that didn't do it either:

    AlterColumn("dbo.ProductTypes", "ProductTypeId", c => c.Int(nullable: false, identity: false));

Is there another way to tell SQL to remove the Identity?