WebHttpBinding authentication ignored - wcf

Question

I'm trying to use basic HTTP authentication with a REST service, but debugging proxy shows that no authentication headers are sent at all, they are ignored! Here is my code:
WebChannelFactory<IMyService> factory = new WebChannelFactory<IMyService>(
new WebHttpBinding(),
new Uri("http://10.6.90.45:8081"));
WebHttpBinding http = (WebHttpBinding) factory.Endpoint.Binding;
http.Security.Transport.ClientCredentialType = HttpClientCredentialType.Basic;
http.Security.Mode = WebHttpSecurityMode.TransportCredentialOnly;
factory.Credentials.UserName.UserName = "username";
factory.Credentials.UserName.Password = "password";
IMyService proxy = factory.CreateChannel();
proxy.SomeMethod();
...
The HTTP request is unauthorized with client authentication scheme 'Basic'. The authentication header received from the server was ''.
Server stack trace:
at System.ServiceModel.Channels.HttpChannelUtilities.ValidateAuthentication(HttpWebRequest request, HttpWebResponse response, WebException responseException, HttpChannelFactory factory)
at System.ServiceModel.Channels.HttpChannelUtilities.ValidateRequestReplyResponse(HttpWebRequest request, HttpWebResponse response, HttpChannelFactory factory, WebException responseException, ChannelBinding channelBinding)
at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)
at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
...