TouchDB Query view MarshalDirectiveException

I'm trying to query a view using TouchDB. I used the binding between TouchDB and MonoTouch available here : https://github.com/mono/monotouch-bindings/tree/master/Couchbase

When the emit delegate method is called, I get a "System.Runtime.InteropServices.MarshalDirectiveException" saying "The type MonoTouch.Foundation.NSObject which is passed to unmanaged code must have a StructLayout attribute."

I found this bug report here : https://bugzilla.xamarin.com/show_bug.cgi?id=4781 that is similar to my problem but there isn't any updates since July 27, 2012.

Here's my test code :

CouchTouchDBServer server = new CouchTouchDBServer ();
CouchDatabase database = server.GetDatabase ("grocery-sync");
database.TracksChanges = true;

// Create a test view
design = database.DesignDocumentWithName ("grocery");
design.DefineView ("testView", (doc,emit) => {
    emit (doc, doc); // Crashes here
}, "1.0");

// Query the view
CouchQuery query = design.CereateQuery("testView");
RestOperation op = query.Start();
string response = op.ResponseBody.AsString;
Console.WriteLine(response);

Has anyone successfully queried a view on TouchDB with MonoTouch? Thanks for your help