Attempting to JIT compile method SWIGStringHelper.CreateString

I'm getting this exception on Xamarin.iOS 6.4.3.0. This code used to work fine in Xamarin.iOS 6.2.x, but now throws this error in 6.4.x.

I know that there are limitations with JIT compiling on iOS, so my code looks like this:

protected class SWIGStringHelper {

    public delegate string SWIGStringDelegate(string message);
    static SWIGStringDelegate stringDelegate = new SWIGStringDelegate(CreateString);

    [DllImport("__Internal", EntryPoint="SWIGRegisterStringCallback_psconnectul")]
    public static extern void SWIGRegisterStringCallback_psconnectul(SWIGStringDelegate stringDelegate);

    [MonoTouch.MonoPInvokeCallback (typeof (SWIGStringDelegate))]
    static string CreateString(string cString) {
      return cString;
    }

    static SWIGStringHelper() {
      SWIGRegisterStringCallback_psconnectul(stringDelegate);
    }
  }

It seems like something is broken with the [MonoPInvokeCallback] attribute. Is there a workaround for this or a fix in the pipeline? Please advise.

Full exception:

InnerException  {System.ExecutionEngineException: Attempting to JIT compile method '(wrapper native-to-managed)
 PointSync.Connect.Ultralite.Native.psconnectulPINVOKE/SWIGStringHelper:CreateString (intptr)' while running 
with --aot-only. See http://docs.xamarin.com/ios/about/limitations for more information.    
at (wrapper managed-to-native) object:__icall_wrapper_mono_delegate_to_ftnptr (object)   
at (wrapper managed-to-native) PointSync.Connect.Ultralite.Native.psconnectulPINVOKE/SWIGStringHelper:SWIGRegisterStringCallback_psconnectul
 (PointSync.Connect.Ultralite.Native.psconnectulPINVOKE/SWIGStringHelper/SWIGStringDelegate)   
at PointSync.Connect.Ultralite.Native.psconnectulPINVOKE+SWIGStringHelper..cctor () [0x00000] 
in <filename unknown>:0 }   
System.ExecutionEngineException