NServiceBus Test.Initialize() given key was not present

I was wondering if anyone knows of this issue when attempting to unit test NServiceBus.

Realise I have two initialize methods below but this is to illustrate what I am trying to do.

Should mention seen these posts which I am not sure are up to date:

http://ift.tt/1Gus4Qa http://ift.tt/1vyQmXX

public static class CustomInit
    {
        public static void Init()
        {
            //Previous versions of NBUS, specifically 4.6.5
            //MessageConventionExtensions.IsEventTypeAction = MessageConfiguration.ForEvents();
            //MessageConventionExtensions.IsCommandTypeAction = MessageConfiguration.ForCommands();            

            //New 5.2.0 how to setup tests
            Test.Initialize(x => x.AssembliesToScan(GetAssembliesToScan()));

            Test.Initialize(
                x =>
                {
                    x.Conventions().DefiningCommandsAs([my namespaces]);
                    x.Conventions().DefiningEventsAs();
                    x.AssembliesToScan(GetAssembliesToScan());
                });
        }

        private static IEnumerable<Assembly> GetAssembliesToScan()
        {
            return new[]
            {
                AssemblyFromType<ISomeInterface>()
            };
        }
}