Problem with MassTransit deserialization

Okay so I have a problem with using MassTransit and it’s deserialization.

We’re publishing messages into a specific queue with RabbitMQ, which should then be further processed by our background services using MassTransit.

The string coming in through the queue looks as following

{

  "routingKey": "article.put",

  "responseQueue": {

    "exchange": "testexchange_gateway",

    "responseRoutingKey": "gatewayResponseQueue",

    "vhost": "testvhost"

  },

  "deviceProperties": {

    "deviceType": "DESKTOP",

    "deviceSize": {

      "width": 10,

      "height": 10

    },

    "javascriptEnabled": false

  },

  "action": "PUT",

  "transactionId": "62b6174d-04b7-4937-b617-4d04b70937b0",

  "contentType": "application/json",

  "body": "Testmessage published while running"

}

With the Contract looking like

public interface IMessage
   {
       string routingKey { get; set; }
       ResponseQueue responseQueue { get; set; }
       DeviceProperties deviceProperties { get; set; }
       string action { get; set; }
       string transactionId { get; set; }
       string contentType { get; set; }
       string body { get; set; }
   }

public interface ResponseQueue
    {
        string exchange { get; set; }
        string responseRoutingKey { get; set; }
        string vhost { get; set; }
    }

 public interface DeviceProperties
    {
        string deviceType { get; set; }
        DeviceSize deviceSize { get; set; }
        bool javascriptEnabled { get; set; }

    }

    public interface DeviceSize
    {
        int width { get; set; }
        int height { get; set; }
    }

My problem now is, whenever I want to consume that message using MassTransit, I will get an error in my _error queue:

MT-Fault-ExceptionType: | System.ArgumentNullException
-- | --
Value cannot be null. Parameter name: source
at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source) at MassTransit.Serialization.JsonConsumeContext..ctor(JsonSerializer deserializer, IObjectTypeDeserializer objectTypeDeserializer, ReceiveContext receiveContext, MessageEnvelope envelope) at MassTransit.Serialization.JsonMessageDeserializer.MassTransit.IMessageDeserializer.Deserialize(ReceiveContext receiveContext)

which I don’t quite understand, as all values needed should be right there.

My consumer:

class ArticleGetConsumer : IConsumer<IMessage>
    {
        public Task Consume(ConsumeContext<IMessage> context)
        {
            var routingKey = context.Message.routingKey;
            return Task.FromResult(0);
        }
    }