MassTransit connecting to RabbitMQ vhost starting with slash - rabbitmq

Question

I am currently trying to implement RabbitMQ in .NET Core 3.1 using MassTransit. I am running into an issue getting started, the RabbitMQ server is running 3.8.5 and Erlang 22.0.7.
The issue occurs during the connection to the RabbitMQ Server. The vhost starts with a / and according the documentation
RabbitMQ URI Specification Image
That should be percent encoded into the URI as %2f
public void ConfigureServices(IServiceCollection services)
{
...
services.AddMassTransit(x =>
{
x.AddConsumer<RequestConsumer>();
x.AddBus(provider =>
{
var bus = Bus.Factory.CreateUsingRabbitMq(cfg =>
{
var uri = new Uri("amqps://rmq.domain.net:5671/%2ftestvhost");
cfg.Host(uri, host =>
{
host.Username("testuser");
host.Password("testpassword");
});
});
return bus;
});
});
services.AddMassTransitHostedService();
}
After attempting to run the connection is closed and the following error is outputted
---> RabbitMQ.Client.Exceptions.OperationInterruptedException: The AMQP operation was interrupted: AMQP close-reason, initiated by Peer, code=530, text='NOT_ALLOWED - vhost %2ftestvhost not found', classId=10, methodId=40
The output from the rabbitmq server is
[error] <0.11481.4> Error on AMQP connection <0.11481.4> (IP -> IP - iisexpress, user: 'testuser', state: opening):
vhost %2ftestvhost not found
[info] <0.11481.4> closing AMQP connection <0.11481.4> (IP -> IP - iisexpress, vhost: 'none', user: 'testuser')
The final message about vhost being 'none' is a little interesting I suspect that 'none' is a default for unknown vhosts.
My question is am I missing something, the URI doesn't seem to map properly to the vhost?
Is their an explicit setting I am missing for a vhost starting with a slash?
I've tried
Adding a second slash in the front
Changing the configuration to use cfg.Host(hostname, port, vhost)