WP8 Compile issue

The dev branch seems to be broken if you try and compile in WIndows Phone 8.1 it brings up the following compile error

Cannot resolve dependency to assembly ‘System.Runtime.InteropServices, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ because it has not been preloaded. When using the ReflectionOnly APIs, dependent assemblies must be pre-loaded or loaded on demand through the ReflectionOnlyAssemblyResolve event
I have tried switching back to 8.0 andit all compiles