RavenDB OnBeforeStore does not fire using BulkInsert

I cannot get OnBeforeStore to fire using a BulkInsert.

It fires fine during a regular Store operation.

I'm trying to use an Invoice number generator to add a formatted number and I'd like to do that in OnBeforeStore.

See code example:

static async Task GenerateInvoiceTest()
{
    using var store = new DocumentStore
    {
        Urls = new string[] { "https://localhost:8080" },
        Database = "APC",
    };

    //this never fires using BulkInsert
    store.OnBeforeStore += (s, e) =>
    {
        if (!(e.Entity is Invoice invoice)) return;
        if (invoice.InvoiceNumber != 0) return;
        invoice.InvoiceNumber = new Random().Next(1, 1000);
    };

    store.Initialize();

    //sample invoices
    var invoices = new List<Invoice>
    {
        new Invoice { StartDate = DateTime.Now, EndDate = DateTime.Now.AddDays(3) },
        new Invoice { StartDate = DateTime.Now, EndDate = DateTime.Now.AddDays(3) },
    };

    //bulk insert test
    using var session = store.OpenAsyncSession();
    using var bulkInsert = store.BulkInsert();
    invoices.ForEach(i => bulkInsert.Store(i));            
    
    //this does NOT fire OnBeforeStore
    await session.SaveChangesAsync();
    
    foreach (var invoice in invoices)
    {
        //always prints 0
        Console.WriteLine(invoice.InvoiceNumber);
    }

    //regular test
    var otherInvoice = new Invoice { StartDate = DateTime.Now, EndDate = DateTime.Now.AddDays(3) };

    await session.StoreAsync(otherInvoice);

    //this DOES fire OnBeforeStore
    await session.SaveChangesAsync();
}