REST API 400 Error on Wiki Page Creation

I have been staring at this for a bit and have no idea where I went wrong. I am trying to create a new Wiki page using the REST API in a C# console app and I am getting a 400 error. Any insight into why would be most appricated!

                            var newTopic = host.PostToXml(2, "wikis/" + wikiID + "/pages.xml", null, true, new RestPostOptions()
                            {
                                PostParameters = new System.Collections.Specialized.NameValueCollection
                            {
                                { "Title", topic},
                                { "wikiid", wikiID.ToString()}
                            }
                            });

...