EF add-migration generates empty migration

I added into my model a new table:

public DbSet<ReturnedTransactions> ReturnedTransactions { get; set; }

And i want my migrations to generate that table for me, so i did:

PM> Add-migration returnedTransactions

And it generated

public partial class returnedTransactions : DbMigration
{
    public override void Up()
    {
    }

    public override void Down()
    {
    }
}

How do i force this thing to generate proper code for me?