RestKit not inverse mapping date

Question

Restkit is mapping my date just fine to an object, but when trying to do an inverse mapping back to json i'm getting this error:

    *** Terminating app due to uncaught exception 'NSInvalidArgumentException', 
    reason: 'Invalid type in JSON write (__NSDate)'

Obviously this is an issue with the json parser for iOS, but I figured the inverse should be handled by RestKit as well. Anyone else experience this or have a solution?

In logging restkit I get this message right before:

D restkit.object_mapping:RKMappingOperation.m:920 Finished mapping operation successfully...

**EDIT:

Mapping example:

// Define media mapping
       RKObjectMapping *mediaMapping = [Media getObjectMapping];

       // Define Post mapping
       RKObjectMapping *postMapping = [RKObjectMapping mappingForClass:[self class]];

       [postMapping addAttributeMappingsFromDictionary:@{
        @"post_id":    @"postID",
        @"userID":     @"userID",
        @"title":      @"title",
        @"favorite":   @"favorite",
        @"created":    @"created",
        @"modified":   @"modified"}];

       // Define relationship in the mapping between Media and Post
       [postMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"media"
                                                                                   toKeyPath:@"media"

                                                                                 withMapping:mediaMapping]];

Discriptor example:

RKObjectMapping *entityMapping = [object getObjectMapping];

RKResponseDescriptor *successDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:entityMapping
                                                                                        method:RKRequestMethodPOST
                                                                                   pathPattern:request.URL.relativePath
                                                                                       keyPath:nil
                                                                                   statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

**UPDATE2:

Right from the dictionary I break point and inspected the offending value in the destination object. [11] = @"created" : 2014-04-21 11:04:43 PDT
key __NSCFConstantString * @"created" 0x002d3818 value __NSDate * 2014-04-21 11:04:43 PDT 0x155bab10

I can see the issue, it appears to be passing the dictionary with the NSDate to [NSJSONSerialization dataWithJSONObject: options: error:] via this method, [RKSerialization dataFromObject: error;

Should RestKit not be converting the NSDate using the RKValueTransformer I have defined before passing to NSJSONSerialization?

Open issue at github can be found here.