Linking issue

Hi,

I'm getting a linking error and I've not idea where it is coming from as I've not used anything that references it. The error I'm seeing is

Error MT2002: Failed to resolve "System.Dynamic.IDynamicMetaObjectProvider" reference from "System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" (MT2002)

I've searched around other than one link that suggests an issue with System.Core can't find anything.

Is there a work around for this or do I need to copy System.Dynamic from somewhere? I'm on the alpha channel using XS 4.1.9 and Xam.iOS 6.4.1.1 (mono 3.2.1)

Paul