Why are .NetStandard 1.0 libraries not working?

I have tried to compile dlls to be used in Unity, however I seem to be getting the error: Assets/Test.cs(12,18): error CS0012: The type `System.Object' is defined in an assembly that is not referenced. Consider adding a reference to assembly `System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' If I build the library as net35 or net46, using the .csproj file, the library works, however, I was lead to believe that netstandard 1.0 libraries work on all implementations, or at the very least, net4.6 equivalent. I have set the player settings to net4.6 in unity. How do I reference this 'System.Object' the error mentions? Thank you, Ramon