Object Reference error updating Xamarin.Forms to 1.5.1.6471

Hi All,

I'm using NuGet to update my Xamarin.Forms application to 1.5.1.6471 (I'm on a 1.4 version) and am experiencing an object reference not set to instance of an object error when doing so. Has anybody else experienced this and is there a workaround? My NuGet update log is below it's all I have to go on.

Thanks

Updating Xamarin.Forms...
Downloading Xamarin.Forms 1.5.1.6471...
Object reference not set to an instance of an object